Tunable electrical field for aggregating microorganisms

ABSTRACT

Described herein are systems, methods, and apparatuses for aggregating microorganism in an aqueous suspension. In particular, are systems, methods, and apparatuses that apply an electrical field to an aqueous suspension comprising microorganisms as the aqueous suspension follows a flow path to cause aggregation of the microorganisms. The electrical field may be continuous or pulsed. In some embodiments, the flow path for the aqueous suspension may vary. In some embodiments, the cross-sectional area of the electrical field may be tuned.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation-in-part ofU.S. Ser. No. 13/733,217, filed Jan. 3, 2013 and entitled “Systems,Methods and Apparatuses For Aggregating And Harvesting MicroorganismsFrom An Aqueous Suspension,” the entire contents of which, including theclaims, are incorporated herein by reference. This application claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Application No.61/707,249, filed Sep. 28, 2012 and entitled “Systems, Methods andApparatuses For Aggregating And Harvesting Microorganisms From AnAqueous Suspension,” the entire contents of which are incorporatedherein by reference. This application claims priority under 35 U.S.C.§119(e) to U.S. Provisional Application No. 61/670,888, filed Jul. 12,2012, and entitled “Systems, Methods and Apparatuses For Aggregating AndHarvesting Microorganisms From An Aqueous Suspension,” the entirecontents of which are incorporated herein by reference.

BACKGROUND

The viability and promise of microorganisms, such as but not limited toalgae, microalgae, and cyanobacteria, as a source of intracellularproducts, such as but not limited to lipids, pigments, and proteins,depends on the ability to: 1) efficiently separate the microorganismsfrom a liquid suspension, and 2) efficiently extract the intracellularproducts from the microorganism. If the microorganisms can beefficiently separated from the liquid suspension for extraction, theintracellular products can be used in a variety of products includingfood, feed, fuel, pharmaceuticals, cosmetics, industrial products,synthesized oil, and fertilizers. Extracting intracellular products frommicroorganisms in an aqueous suspension is inefficient because of thelow density of organisms and complications from the high amounts ofwater and other constituents of the aqueous suspension. Aggregating themicroorganisms and separating the aggregation of organisms from theaqueous suspensions allows for a more efficient extraction process.Current methods of aggregating microorganisms in an aqueous suspensioninclude using chemicals which provide complications in the extractionprocess, and extended periods of time to dry microorganisms or evaporatethe water from the aqueous suspension. Such drying or evaporationtechniques inhibit the overall speed of the process. Therefore there isa need for a simple and efficient method of aggregating and separatingmicroorganisms from an aqueous suspension.

SUMMARY OF THE INVENTION

According to various embodiments, the systems, methods and apparatusesof this disclosure generally involve subjecting particles such asmicroorganisms, particularly algae, microalgae and cyanobacteria, in anaqueous suspension to an electrical current creating an electricalfield, electromagnetic field, or acoustic energy field. In someembodiments, the electrical current may be supplied in a constant orcontinuous manner, such as by direct current. In some embodiments, theelectrical current may be a pulsed electrical current and varysinusoidally, such as in an alternating current. The application of anelectrical field causes a change in the surface charge of themicroorganisms, which induces the aggregation of the microorganisms intoa larger mass through coagulation or flocculation. The application ofacoustic energy causes the microorganisms to concentrate at locations ofminimum pressure. These methods of aggregation are achieved withoutdisrupting and/or lysing the cell wall or cell membrane of themicroorganisms. The aggregated, larger mass is then separated from theaqueous suspension for further processing, such as, but not limited, toan extraction process.

According to some embodiments, the aggregation is achieved by flowing anaqueous suspension containing microorganisms through a channel whilesimultaneously applying the electrical current as mentioned above.According to various embodiments, the electrical field intensity,electrical field cross-section, flow rate, and channel dimensions areselected in combination with the particular composition of the aqueoussuspension to aggregate the microorganisms without lysing or otherwisedisrupting the cells of the microorganisms. After aggregation, a portionof the water can be removed from the aqueous suspension by methods suchas, but not limited to, decanting and skimming, to produce aconcentrated microorganism slurry, which can then be used as input foran extraction process.

According to some embodiments, aggregation using electrical fieldsfacilitates subsequent extraction processes by producing a moreconcentrated microorganism slurry and reducing the amount of the liquidculture medium in the extraction process. In some embodiments, theconcentration of the slurry can be greater than 1% solids while in otherembodiments the concentration is greater than 3% or greater than 5%, orin a range from 1% to 30% solids by weight.

In some embodiments, the present invention relates to a system thatincludes a first apparatus configured to perform aggregation with anelectric field to produce an aggregated slurry as discussed above. Insome embodiments, the aggregated slurry is in fluid communication with aseparation apparatus for separating water from the aggregatedmicroorganisms to produce a concentrated microorganism slurry. In theseparation apparatus the aggregated microorganisms may continue toaggregate with other microorganisms in the aqueous suspension to form alarger aggregated mass. The aggregated mass of microorganisms may sinkto the bottom of the separation apparatus or float to the surface of theliquid medium in the separation apparatus to facilitate recovery andseparation of the aggregated mass of microorganisms. In variousembodiments, the aggregated microorganisms exiting the electrical fieldmay be further aggregated by subjecting the microorganisms to multiplepasses in the electrical field or a new electrical field.

According to some embodiments of either the systems and/or the methodsdescribed previously, regulation of the electrical energy applied to themicroorganism(s), such as algae cells, can be controlled by adjusting atleast one of the voltage, current, electrical field cross sectionalarea, pulsation frequency, residence time, flow rate, flow path channeldimensions, and combinations thereof, so that the microorganism(s)is/are subjected to the electrical field in a manner sufficient toachieve the desired effect of aggregating the microorganisms. In thisway, according to such embodiments, the microorganisms can beefficiently harvested and dewatered with an efficient use of externalenergy, which can be accurately controlled and adjusted to create thedesired effect or degree of aggregation and/or harvesting. In someadditional embodiments, control can be affected manually. In otherembodiments, however, the control can be affected automatically with theaid of a computerized sensor and control system. Suitable sensors can beused to measure the rate and/or amount of aggregation and provide outputsignals to the computer to control the variables of voltage, current,electrical field cross sectional area, pulsation frequency, residencetime, flow rate, and flow path channel dimensions that themicroorganisms are subjected to. Such sensors may comprise, but are notlimited to, turbidity, density, flow rate, chlorophyll a, opticaldensity, electrical current, and electrical voltage sensors. In onenon-limiting example turbidity or density sensors can measure the slurrybefore entering the electrical field and exiting the electrical field todetermine and the amount of the aqueous suspension to be separated forfurther aggregation in a separate apparatus, recycled to the sameapparatus for further aggregation, or separated to flow to the otherprocessing paths, such as to the separation apparatus.

According to various embodiments, electrical input frequency rates aredetermined by biomass density of the microorganisms with pulse ratefrequencies being generally increased/decreased proportionally with anincrease/decrease in biomass density. In some embodiments, biomassdensity is determined by using a formula or algorithm comprising apercentage of grams of biomass present per liter of flowing liquidmedium. The formula or algorithm can be utilized in the computer basedsensor and control system to determine the desired operating parametersby matching the formula or algorithm value to corresponding, operatingparameters residing in a matrix of operating parameters and measuredeffects.

In some embodiments, a separation apparatus is in fluid communicationdownstream of the aggregating apparatus applying an electrical field,such that the aqueous suspension can flow through electrical field intothe separation apparatus. In some embodiments, the separation apparatusapplies acoustic energy to the aqueous suspension. In some embodiments,the separation apparatus comprises a foam fractionation deviceconfigured to mix the aqueous suspension containing aggregatedmicroorganisms with an injected gas to produce a gas and liquid mixture,and collect a foam comprising aggregated microorganisms. In someembodiments, the separation apparatus is a separation tank. According toat least one embodiment, an element is disposed in the separation tankfor producing bubbles or microbubbles. In some embodiments, an aqueoussuspension containing aggregated microorganisms is disposed in the flowpath of the microbubbles and optionally a pump is disposed in theseparation tank for circulating the aqueous suspension. In yet furtherembodiments, the method further includes the steps of (1) applying asufficient amount of an electrical current to the aqueous suspension foraggregating the microorganisms, (2) flowing the aqueous suspensioncontaining the electrically treated microorganisms to the separationtank, (3) activating the pump and the element for producing microbubblesresulting in a plurality of microbubbles that impinge upon theaggregated microorganisms so as to cause such microorganisms to floatupwards in the aqueous suspension, and (4) separating the floatingaggregated microorganisms from the aqueous suspension. In variousembodiments, the element disposed in the separation tank for producingmicrobubbles can be any suitable device or apparatus, e.g. a mixer, afluidic oscillator, a bubble generator or a microbubble generator.

One aspect of this disclosure provides an apparatus for aggregatingmicroorganisms in an aqueous suspension. The apparatus comprises atleast one cathode disposed opposite at least one anode, and at least onepair of spaced insulators disposed between the at least one cathode andthe at least one anode. The apparatus also comprises a channel definedbetween the at least one cathode, at least one anode, and the at leastone pair of spaced insulators. The channel has a length commensuratewith the lengths of the at least one cathode and at least one anode. Thechannel defines a fluid flow path for the aqueous suspension to flowthrough. The channel comprises a cross-section comprising a height andwidth. At least one of the height and the width of the cross-section ofthe channel varies over a length of the channel. The apparatus alsocomprises an electrical power source that is operably connected to theat least one cathode and the at least one anode. When an electriccurrent is applied from the electrical power source to the at least onecathode and the at least one anode, an electrical field is created. Theapparatus also comprises a separation tank that is in fluidcommunication downstream with the channel. The separation tank isconfigured to collect fluid flow from the fluid flow path defined by thechannel.

In some embodiments, at least one of the height and width of thecross-section of the channel increases over the length of the fluid flowpath. In some embodiments, at least one of the height and the widthdecreases of the cross-section of the channel decreases over the lengthof the fluid flow path.

In some embodiments, the length of the channel may expand or contract.In some embodiments, the apparatus comprises a series of channels ofdifferent cross-section size defined by cathodes, anodes, and pairs ofinsulators, wherein the channels are coupled together in a telescopingconfiguration. In some embodiments, the cathode, anode, and pair ofinsulators are disposed within a housing.

In some embodiments, the electrical power source provides continuouselectrical current. In some embodiments, the electrical power sourceprovides pulsed electrical current. In some embodiments, the intensityof the electrical current may be changed.

Another aspect of this disclosure is directed to an apparatus foraggregating microorganisms in an aqueous suspension comprising a firstelectrical conductor disposed within a second electrical conductor,wherein a channel is defined between an exterior surface of the firstelectrical conductor and an interior surface of the second electricalconductor. The channel defines a fluid flow path for the aqueoussuspension. The channel comprises a cross-section comprising a diameterand that diameter varies over a length of the fluid flow path. Theapparatus also comprises an electrical power source operably connectedto the first electrical conductor and the second electrical conductor.The first electrical conductor is configured as either an anode or acathode. The second electrical conductor is configured as either ananode or a cathode and is not the same as the first electrical conductor(e.g., if the first electrical conductor is configured as an anode, thenthe second electrical conductor is configured as a cathode; if the firstelectrical conductor is configured as a cathode, then the secondelectrical conductor is configured as an anode). When an electricalcurrent is applied from the electrical power source to the firstelectrical conductor and the second electrical conductor, an electricalfield is created. The apparatus also comprises a separation tank influid communication downstream with the channel. The separation tank isconfigured to collect fluid flow from the fluid flow path defined by thechannel.

In some embodiments, the diameter of the cross-section increases over alength of the channel. In some embodiments, the diameter of thecross-section decreases over a length of the channel.

In some embodiments, the length of the channel may expand or contract.

In some embodiments, the apparatus comprises a series of channels ofdifferent cross-section size defined by first and second electricalconductors and pairs of insulators, wherein the channels are coupledtogether in a telescoping configuration. In some embodiments, the firstelectrical conductor, the second electrical conductor, and pair ofinsulators are disposed within a housing.

In some embodiments, the electrical power source provides continuouselectrical current. In some embodiments, the electrical power sourceprovides pulsed electrical current.

Another aspect of this disclosure is directed to a method foraggregating microorganisms in an aqueous suspension. In the method, anaqueous suspension comprising microorganisms is flowed into at least oneapparatus. The apparatus comprises at least one cathode disposedopposite at least one anode, and at least one pair of spaced insulatorsdisposed between the at least one cathode and the at least one anode.The apparatus also comprises a channel defined between the at least onecathode, at least one anode, and the at least one pair of spacedinsulators. The channel has a length commensurate with the lengths ofthe at least one cathode and at least one anode. The channel defines afluid flow path for the aqueous suspension to flow through. The channelcomprises a cross-section comprising at least one of a height, width,and diameter. At least one of the height, width, and diameter of thecross-section of the channel varies over at least a portion of thelength of the fluid flow path. The apparatus also comprises anelectrical power source that is operably connected to the at least onecathode and the at least one anode. When an electric current is appliedfrom the electrical power source to the at least one cathode and the atleast one anode, an electrical field is created. The apparatus alsocomprises a separation tank that is in fluid communication downstreamwith the channel. The separation tank is configured to collect fluidflow from the fluid flow path defined by the channel. In the method,after flowing the aqueous suspension comprising microorganisms into atleast one apparatus, the aqueous suspension is then flowed through thechannel and into the separation tank. An electrical current is appliedfrom the electrical power source to the at least one cathode and the atleast one anode, thereby creating an electrical field in the channel,wherein the surface charge of the microorganisms in the aqueoussuspension in the fluid flow path is treated, and wherein themicroorganisms aggregate with similarly treated microorganisms in theaqueous suspension without disrupting the cell membranes of themicroorganisms. The microorganisms are aggregated in the separationtank. Then, the aggregated microorganisms are separated from the aqueoussuspension in the separation tank.

In some embodiments, the at least one apparatus used in the methodcomprises a plurality of apparatuses in parallel configuration. In someembodiments, the at least on apparatus comprises a plurality ofapparatuses in a series configuration. In some embodiments, the at leaston apparatus comprises a plurality of apparatuses in a combination ofparallel and series configurations.

In some embodiments, the electrical power source provides continuouselectrical current. In some embodiments, the electrical power sourceprovides pulsed electrical current.

Another aspect of this disclosure is directed to a system foraggregating microorganisms in an aqueous suspension comprising aplurality of aggregating apparatuses. Each aggregating apparatuscomprises at least one electrical conductor comprising a conductivematerial configured as a cathode and at least one electrical conductorcomprising conductive material configured as an anode. The electricalconductor comprising a conductive material configured as a cathode isdisposed opposite the at least one electrical conductor comprisingconductive material configured as an anode. Each apparatus alsocomprises at least one pair of spaced insulators disposed between the atleast one electrical conductor comprising a conductive materialconfigured as a cathode and the at least one electrical conductorcomprising a conductive material configured as an anode. Each apparatusalso comprises a channel defined between the at least one electricalconductor comprising a conductive material configured as a cathode, atleast one electrical conductor comprising a conductive materialconfigured as an anode, and the at least one pair of spaced insulators.The channel has a length commensurate with the lengths of the at leastone electrical conductor comprising a conductive material configured asa cathode and the at least one electrical conductor comprising aconductive material configured as an anode. The channel defines a fluidflow path for the aqueous suspension to flow through. The channelcomprises a cross-section comprising at least one of a height, width,and diameter. At least one of the height, width, and diameter of thecross-section of the channel varies over at least a portion of thelength of the fluid flow path. The apparatus also comprises anelectrical power source that is operably connected to the at least oneelectrical conductor comprising a conductive material configured as acathode and the at least one electrical conductor comprising aconductive material configured as an anode. When an electric current isapplied from the electrical power source to the at least one electricalconductor comprising a conductive material configured as a cathode andthe at least one electrical conductor comprising a conductive materialconfigured as an anode, an electrical field is created. In this system,at least one of the aggregating apparatuses differs from at least oneother aggregating apparatus by at least one characteristic selected fromthe group consisting of the conductive material of the at least oneelectrical conductor comprising a conductive material configured as acathode, the conductive material of the at least one electricalconductor comprising a conductive material configured as an anode, theintensity of the electrical field, the fluid flow path height, the fluidflow path width, the fluid flow path diameter, and the length of thechannel.

In some embodiments, the conductive material is selected from the groupconsisting of aluminum, copper, titanium, nickel, steel, stainlesssteel, graphite, and a conductive polymer. In some embodiments, theconductive material comprises a coating of at least one of iridium,ruthenium, platinum, rhodium, tantalum, and a mixed metal polymer.

In some embodiments, the system comprises a plurality of aggregatingapparatuses configured in parallel. In some embodiments, the systemcomprises a plurality of aggregating apparatuses configured in series.In some embodiments, the system comprises a plurality of aggregatingapparatuses configured in a combination of parallel and seriesconfigurations.

In some embodiments, the electrical power source provides continuouselectrical current. In some embodiments, the electrical power sourceprovides pulsed electrical current. In some embodiments, at least one ofthe aggregating apparatuses differs from at least one other aggregatingapparatus by electrical pulse type.

Another aspect of this disclosure is directed to a method foraggregating microorganisms in an aqueous suspension, the methodcomprising flowing an aqueous suspension comprising microorganisms intoan aggregating apparatus or a plurality of aggregating apparatuses. Eachaggregating apparatus comprises at least one electrical conductorcomprising a conductive material configured as a cathode and at leastone electrical conductor comprising conductive material configured as ananode. The electrical conductor comprising a conductive materialconfigured as a cathode is disposed opposite the at least one electricalconductor comprising conductive material configured as an anode. Eachapparatus also comprises at least one pair of spaced insulators disposedbetween the at least one electrical conductor comprising a conductivematerial configured as a cathode and the at least one electricalconductor comprising a conductive material configured as an anode. Eachapparatus also comprises a channel defined between the at least oneelectrical conductor comprising a conductive material configured as acathode, at least one electrical conductor comprising a conductivematerial configured as an anode, and the at least one pair of spacedinsulators. The channel has a length commensurate with the lengths ofthe at least one electrical conductor comprising a conductive materialconfigured as a cathode and the at least one electrical conductorcomprising a conductive material configured as an anode. The channeldefines a fluid flow path for the aqueous suspension to flow through.The channel comprises a cross-section comprising at least one of aheight, width, and diameter. At least one of the height, width, anddiameter of the cross-section of the channel varies over at least aportion of the length of the fluid flow path. The apparatus alsocomprises an electrical power source that is operably connected to theat least one electrical conductor comprising a conductive materialconfigured as a cathode and the at least one electrical conductorcomprising a conductive material configured as an anode. When anelectric current is applied from the electrical power source to the atleast one electrical conductor comprising a conductive materialconfigured as a cathode and the at least one electrical conductorcomprising a conductive material configured as an anode, an electricalfield is created. In this system, at least one of the aggregatingapparatuses differs from at least one other aggregating apparatus by atleast one characteristic selected from the group consisting of theconductive material of the at least one electrical conductor comprisinga conductive material configured as a cathode, the conductive materialof the at least one electrical conductor comprising a conductivematerial configured as an anode, the intensity of the electrical field,the fluid flow path height, the fluid flow path width, the fluid flowpath diameter, and the length of the channel. In the method, the aqueoussuspension comprising microorganisms flows through the channel into aseparation tank. An electrical current is applied from the electricalpower source to the at least one electrical conductor comprising aconductive material configured as a cathode and the at least oneelectrical conductor comprising a conductive material configured as ananode, wherein an electrical field comprising an intensity is created,wherein the electrical field treats the surface charges of themicroorganisms and causes similarly treated microorganisms to aggregatein the aqueous suspension without disrupting the cell membranes. Next,the microorganisms are aggregated in the separation tank. Then, theaggregated microorganisms are separated from the aqueous suspension inthe separation tank.

In some embodiments, the conductive material is selected from the groupconsisting of aluminum, copper, titanium, nickel, steel, stainlesssteel, graphite, and a conductive polymer. In some embodiments, theconductive material comprises a coating of at least one of iridium,ruthenium, platinum, rhodium, tantalum, and a mixed metal polymer.

In some embodiments, the system comprises a plurality of aggregatingapparatuses configured in parallel. In some embodiments, the systemcomprises a plurality of aggregating apparatuses configured in series.In some embodiments, the system comprises a plurality of aggregatingapparatuses configured in a combination of parallel and seriesconfigurations.

In some embodiments, the electrical power source provides continuouselectrical current. In some embodiments, the electrical power sourceprovides pulsed electrical current. In some embodiments, at least one ofthe aggregating apparatuses differs from at least one other aggregatingapparatus by electrical pulse type.

In some embodiments, the aggregating apparatus further comprises aseparation tank in fluid communication downstream from the channel. Theseparation tank can be configured to collect fluid flow from the fluidflow path defined by the channel.

In some embodiments, at least a portion of the aqueous suspensionexiting the fluid flow path of the apparatus is recirculated backthrough the apparatus.

In some embodiments, the method further comprises measuring with asensor at least one of the density and turbidity of the aqueoussuspension and transmitting the measurement value to a computercontroller. In some embodiments, the computer controller receives themeasurement value from the sensor and, based on that measurement value,can adjust the volume of the portion of the aqueous suspension that isrecirculated through the apparatus. In some embodiments, the portion ofaqueous suspension that is recirculated is mixed with an untreatedvolume of aqueous suspension comprising microorganisms in a continuousaggregation process. In further embodiments, the aqueous suspensionexiting the apparatus is recirculated to the apparatus until themeasurement value reaches a threshold value in a batch aggregationprocess.

Another aspect of this disclosure is directed to an apparatus foraggregating microorganisms in an aqueous suspension. The apparatuscomprises a vessel configured to contain an aqueous suspension ofmicroorganisms and configured for fluid communication with a housing.The apparatus also comprises at least one first electrical conductorconfigured as a cathode disposed within the housing, at least one secondelectrical conductor configured as an anode disposed within the housing,at least one third electrical conductor configured as a collectorelectrode disposed within the housing and adjacent to the at least onefirst electrical conductor, at least one fourth electrical conductorconfigured as a control electrode disposed within the housing andadjacent to the at least one first electrical conductor, wherein the atleast one first electrical conductor is at least partially surrounded bythe at least one second electrical conductor such that a channel isdefined between an exterior surface of the at least one first electricalconductor and an interior surface of the at least one second electricalconductor, providing a fluid flow path configured for receiving theaqueous suspension from the vessel. The apparatus also comprises atleast one electrical power source operably connected to the at least onefirst electrical conductor, second electrical conductor, thirdelectrical conductor, and fourth electrical conductor, wherein anelectrical field is created by providing an electrical current from theelectrical power source to the at least one first electrical conductor,second electrical conductor, third electrical conductor, and fourthelectrical conductor wherein a cross-sectional area of the electricalfield is adjustable based on the current applied to the at least onethird electrical conductor and the at least one fourth electricalconductor.

In further embodiments, the apparatus further comprises a separationtank configured to receive the aqueous suspension exiting the fluid flowpath.

In some embodiments, the at least one first electrical conductor has acircular cross-section or a polygonal cross-section. In someembodiments, the at least one second electrical conductor has a curvedsemi-circular cross-section or a circular cross-section. In someembodiments, the at least one third electrical conductor has a circularcross-section, a polygonal cross-section, a v-shaped cross section, anoval cross-section or a curved cross section. In some embodiments, theat least one fourth electrical conductor has a circular cross-section,oval cross-section or a polygonal cross-section.

In other embodiments, the at least one third electrical conductor andthe at least one second electrical conductor have a positive potentialrelative to the at least one first electrical conductor, the at leastone second electrical conductor has a larger positive potential than theat least one third electrical conductor, and the at least one fourthelectrical conductor has a negative potential relative to the at leastone first electrical conductor.

In some embodiments, the cross-sectional area of the electrical field isadjusted by increasing or decreasing the negative potential of the atleast one third electrical conductor. In other embodiments, thecross-sectional area of the electrical field is adjusted by increasingor decreasing the negative potential of the at least one fourthelectrical conductor. In some embodiments, the cross-sectional area ofthe electrical field is adjusted by increasing or decreasing thenegative potential of the at least one third electrical conductor and atleast one fourth electrical conductor.

In some embodiments, the electrical power source provides continuouselectrical current. In some embodiments, the electrical power sourceprovides pulsed electrical current.

Another aspect of this disclosure is directed to a method foraggregating microorganisms in an aqueous suspension. The methodcomprises flowing an aqueous suspensions comprising microorganisms intoan apparatus. The apparatus comprises at least one electrical conductorwith a first potential, at least one second electrical conductor with asecond potential, at least one third electrical conductor with a thirdpotential, and at least one fourth electrical conductor with a fourthpotential, the at least one first electrical conductor being disposedsuch that a channel is defined between the at least one first electricalconductor and the at least one second electrical conductor, wherein thechannel defines a fluid flow path for the aqueous suspension. Theapparatus also comprises at least one electrical power source operablyconnected to the at least one first electrical conductor, secondelectrical conductor, third electrical conductor, and fourth electricalconductor, wherein an electrical field is created by providing anelectrical current from the electrical power source to the at least onefirst electrical conductor, second electrical conductor, thirdelectrical conductor, and fourth electrical conductor. Next, the methodcomprises applying an electrical current to the at least one firstelectrical conductor, second electrical conductor, third electricalconductor, fourth electrical, and aqueous suspension whereby the surfacecharge of the microorganisms is treated and the microorganisms aggregatewith similarly treated microorganisms in the aqueous suspension withoutdisrupting the cell membrane. The method also comprises adjusting the atleast one power source to change the potential of at least one of thethird electrical conductor and fourth electrical conductor, wherein thechange in potential of the at least one third electrical conductor orfourth electrical conductor changes the cross-sectional area of theelectrical field.

In some embodiments, the at least one third electrical conductor and theat least one second electrical conductor have a positive potentialrelative to the at least one first electrical conductor, the at leastone second electrical conductor has a larger positive potential than theat least one third electrical conductor, and the at least one fourthelectrical conductor has a negative potential relative to the at leastone first electrical conductor. In some embodiments, the electricalpower source provides continuous electrical current. In someembodiments, the electrical power source provides pulsed electricalcurrent.

Another aspect of this disclosure is directed to a method of aggregatingmicroorganisms in an aqueous solution. The method comprises providing anaqueous solution feed comprising a liquid and microorganisms dispersedtherein and aggregating the aqueous suspension feed. The aggregatingcomprises applying a pulsed electric field to the aqueous suspension,the pulsed electrical field generated by a power source and a pulsegenerator, wherein said pulse generator produces a pattern of electricalpulses which vary in a pulse type comprising at least one of a pulseamplitude, a pulse duration, a pulse shape, and a pause duration betweenpulses.

In some embodiments, the pulse shape is rectangular, trapezoidal,exponentially decaying, unipolar, or bipolar. In some embodiments, thepulse duration ranges from 1 to 1,000 nanoseconds. In some embodiments,the pattern of electrical pulses alternates between two pulse types. Insome embodiments, the pattern of electrical pulses comprises more thantwo pulse types. In other embodiments, the pattern of electrical pulsesutilized by the pulse generator comprises a programmed pattern. Infurther embodiments, the programmed pattern is selected by acomputerized controller based on at least one of a measured turbidity ofthe aqueous solution, a measured density of the aqueous solution, acomposition of the aqueous solution, and a flow rate of the aqueoussolution.

Yet another aspect of this disclosure is directed to a system foraggregating microorganisms in an aqueous suspension The system comprisesat least one apparatus comprising at least one electrode, said at leastone electrode in electrical communication with a at least one powersupply and in liquid communication with an aqueous solution feedcomprising microorganisms and a liquid, the at least one power supplycomprising a pulse generator and configured to apply a pattern ofelectrical pulses which vary in a pulse type comprising at least one ofa pulse amplitude, a pulse duration, a pulse shape, and a pause durationbetween pulses, to the aqueous suspension. The system also comprises aseparation tank in fluid communication with the apparatus for receivingthe aqueous suspension after application of the pattern of electricalpulses.

In some embodiments, the pulse shape is rectangular, trapezoidal,exponentially decaying, unipolar, or bipolar. In some embodiments, thepulse duration ranges from 1 to 1,000 nanoseconds. In some embodiments,the pattern of electrical pulses alternates between two pulse types. Infurther embodiments, the pattern of electrical pulses comprises morethan two pulse types. In other embodiments, the pattern of electricalpulses utilized by the pulse generator comprises a programmed pattern.In some embodiments, the programmed pattern is selected by acomputerized controller based on at least one of a measured turbidity ofthe aqueous solution, a measured density of the aqueous solution, acomposition of the aqueous solution, and a flow rate of the aqueoussolution.

Yet another aspect of this disclosure is directed to a system foraggregating microorganisms in an aqueous suspension The system comprisesa device configured to apply an electric field to an aqueous suspension.The device comprises at least one first electrical conductor, at leastone second electrical conductor, wherein the at least one firstelectrical conductor is disposed within the at least one secondelectrical conductor, such that a channel is defined between an exteriorsurface of the at least one first electrical conductor and an interiorsurface of the at least one second electrical conductor and with across-section comprising a diameter, the channel providing a fluid flowpath for the aqueous suspension. The device also comprises an electricalpower source operably connected to the at least one first electricalconductor and the at least one second electrical conductor, whereinelectrical field is created when an electric current is provided fromthe electrical power source to the at least one first electricalconductor and the at least one second electrical conductor and theaqueous suspension. The system also comprises a device configured toapply an acoustic wave to the aqueous suspension, the device comprisinga tube configured to contain a flow of the aqueous suspension, at leastone transducer coupled to the tube, and a generator configured toproduce and transmit electrical radio frequency signals, wherein thegenerator transmits an electrical radio frequency signal to thetransducer and the transducer converts the electrical signal into anacoustic signal which vibrates the tube and creates a wave with apressure minima node at a location within the tube, wherein the deviceconfigured to apply an electrical field and the device configured toapply an acoustic wave to the aqueous suspension are in fluidcommunication, and wherein the device configured to apply an electricalfield and the device configured to apply an acoustic wave to the aqueoussuspension each use pulsed electrical energy.

In some embodiments, the pressure minima node is located at the centralaxis of the tube. In other embodiments, the minima node is located atthe interior wall of the tube. In further embodiments, the systemfurther comprises a collector disposed in the tube configured to receiveand separate a portion of the flow of the aqueous suspension.

In other embodiments, the system further comprises a piezoelectricvibration energy harvester coupled to the tube and configured to convertvibration energy into electrical current. In some embodiments, the waveis a standing wave. In other embodiments, the wave is a traveling wave.

In further embodiments, the device configured to apply an electric fieldfurther comprises at least one third and at least one fourth electricalconductors. In other embodiments, a cross-section of the electricalfield may be adjusted by tuning the electrical conductors. In stillother embodiments, the device is configured to apply an electric fieldfurther comprises a cross section of the flow path which varies over alength of the flow path.

Another aspect of this disclosure is directed to a method of aggregatingmicroorganisms in an aqueous medium. The method comprises flowing anaqueous medium comprising microorganisms of a first type through a firsttube and a second tube. Next, the method comprises applying pulsedacoustic energy to the first tube to generate a standing wave with apressure minima node within the first tube. Then the method comprisesapplying pulsed electrical energy to the second to tube to generate anelectrical field within the second tube.

In some embodiments, the aqueous medium flows through the first tubebefore the second tube, the acoustic energy is applied to the aqueousmedium first to selectively target microorganisms of the first type andconcentrate the microorganisms of the first type at a pressure minimanode, the concentrate of microorganisms of the first type are separatedfrom the aqueous medium by a collector disposed within the first tube,and the electrical energy is applied to the concentrate ofmicroorganisms of the first type to further induce aggregation.

In some embodiments, the aqueous medium flows through the second tubebefore the first tube, the electrical energy is applied to the aqueousmedium first to induce aggregation of the microorganisms of the firsttype, next apply the acoustic energy to the aqueous medium to furtherconcentrate the microorganisms of the first type, separating theaggregated microorganisms of the first type from the aqueous mediumthrough a collector disposed within the first tube, and recycling theaqueous medium for further electrical energy application.

In some embodiments, an electrical field created by the pulse electricalfield may be tuned to adjust a cross section of the electric field. Insome embodiments, a flow path of the second tube may change in crosssection over a length of the second tube.

Another aspect of this disclosure is directed to an apparatus foraggregating microorganisms in an aqueous suspension. The apparatuscomprises a tube configured to contain a flow of an aqueous suspensionscomprising microorganisms, an anode disposed within the tube and with alength parallel to a concentric longitudinal axis of the tube, and acathode disposed within the tube, and with a length parallel to theanode forming a gap between the anode and cathode comprising theconcentric longitudinal axis of the tube. The apparatus also comprisesan electrical power source operably connected to the anode and thecathode for creating an electrical field by providing an electriccurrent that is applied between the anode and cathode and the aqueoussuspension, at least one transducer coupled to the tube, and a generatorconfigured to produce and transmit radio frequency signals. In thisapparatus, the generator transmits an electrical radio frequency signalto the transducer and the transducer converts the electrical signal intoan acoustic signal which vibrates the tube and creates a standing wavewith a pressure minima node at a location between the anode and cathode.

In some embodiments, the electrical field and acoustic standing wave areapplied simultaneously to the aqueous suspension. In some embodiments,the apparatus further comprises a piezoelectric vibration energyharvester coupled to the tube and configured to convert vibration energyinto electrical current. In some embodiments, the electrical field ispulsed. In other embodiments, the acoustic signal is pulsed.

Another aspect of this disclosure is directed to an apparatus foraggregating microorganisms in an aqueous suspension. The apparatuscomprises at least one first electrical conductor configured as acathode, at least one second electrical conductor configured as ananode, and at least one pair of spaced insulators disposed between theat least one first electrical conductor and the at least one secondelectrical conductor, the at least one first conductor being disposedopposite the at least one second electrical conductor, such that achannel is defined between the at least one first electrical conductor,the at least one second electrical conductor, and the at least one pairof spaced insulators, the channel providing a fluid flow path for theaqueous suspension. The apparatus also comprises an electrical powersource operably connected to the at least one first electrical conductorand the at least one second electrical conductor, wherein an electricalfield is created by providing an electric current from the electricalpower source to the at least one first electrical conductor and the atleast one second electrical conductor. The apparatus also comprises atleast one first transducer coupled to the at least one first electricalconductor, at least one second transducer coupled to the at least onesecond electrical conductor, and a generator configured to produce andtransmit electrical radio frequency signals. In the apparatus, thegenerator transmits an electrical radio frequency signal to the at leastone first and second transducers, and the transducers convert theelectrical signal into an acoustic signal which vibrates the at leastone first electrical conductor and the at least one second electricalconductor, and creates a standing wave with a pressure minima node at alocation between the at least one first electrical conductor and the atleast one second electrical conductor.

In some embodiments, the electrical field and acoustic standing wave areapplied simultaneously to the aqueous suspension. In some embodiments,the apparatus further comprises a piezoelectric vibration energyharvester coupled to the at least one first electrical conductor or theat least one second electrical conductor and configured to convertvibration energy into electrical current. In some embodiments, theelectrical field is pulsed. In some embodiments, the acoustic signal ispulsed.

The particles separated by the system of the present invention areusually living organisms or parts of living plant, animal or microbialorganisms. Typically microorganisms and single cell or relatively fewcells clumps, organelles or whole organisms are separated from a liquid.Microorganisms suitable for the systems, methods and apparatusesdescribed comprise, but are not limited to, algae, microalgae, andcyanobacteria. Non-limiting examples of microalgae that can be used withthe methods of the invention are members of one of the followingdivisions: Chlorophyta, Cyanophyta (Cyanobacteria), andHeterokontophyta. In certain embodiments, the microalgae used with themethods of the invention are members of one of the following classes:Bacillariophyceae, Eustigmatophyceae, and Chrysophyceae. In certainembodiments, the microalgae used with the methods of the invention aremembers of one of the following genera: Nannochloropsis, Chlorella,Dunaliella, Scenedesmus, Selenastrum, Oscillatoria, Phormidium,Spirulina, Amphora, and Ochromonas.

Non-limiting examples of microalgae species that can be used with themethods of the present invention include: Achnanthes orientalis,Agmenellum spp., Amphiprora hyaline, Amphora coffeiformis, Amphoracoffeiformis var. linea, Amphora coffeiformis var. punctata, Amphoracoffeiformis var. taylori, Amphora coffeiformis var. tenuis, Amphoradelicatissima, Amphora delicatissima var. capitata, Amphora sp.,Anabaena, Ankistrodesmus, Ankistrodesmus falcatus, Boekeloviahooglandii, Borodinella sp., Botryococcus braunii, Botryococcussudeticus, Bracteococcus minor, Bracteococcus medionucleatus, Carteria,Chaetoceros gracilis, Chaetoceros muelleri, Chaetoceros muelleri var.subsalsum, Chaetoceros sp., Chlamydomas perigranulata, Chlorellaanitrata, Chlorella antarctica, Chlorella aureoviridis, ChlorellaCandida, Chlorella capsulate, Chlorella desiccate, Chlorellaellipsoidea, Chlorella emersonii, Chlorella fusca, Chlorella fusca var.vacuolata, Chlorella glucotropha, Chlorella infusionum, Chlorellainfusionum var. actophila, Chlorella infusionum var. auxenophila,Chlorella kessleri, Chlorella lobophora, Chlorella luteoviridis,Chlorella luteoviridis var. aureoviridis, Chlorella luteoviridis var.lutescens, Chlorella miniata, Chlorella minutissima, Chlorellamutabilis, Chlorella nocturna, Chlorella ovalis, Chlorella parva,Chlorella photophila, Chlorella pringsheimii, Chlorella protothecoides,Chlorella protothecoides var. acidicola, Chlorella regularis, Chlorellaregularis var. minima, Chlorella regularis var. umbricata, Chlorellareisiglii, Chlorella saccharophila, Chlorella saccharophila var.ellipsoidea, Chlorella salina, Chlorella simplex, Chlorella sorokiniana,Chlorella sp., Chlorella sphaerica, Chlorella stigmatophora, Chlorellavanniellii, Chlorella vulgaris, Chlorella vulgaris fo. tertia, Chlorellavulgaris var. autotrophica, Chlorella vulgaris var. viridis, Chlorellavulgaris var. vulgaris, Chlorella vulgaris var. vulgaris fo. tertia,Chlorella vulgaris var. vulgaris fo. viridis, Chlorella xanthella,Chlorella zofingiensis, Chlorella trebouxioides, Chlorella vulgaris,Chlorococcum infusionum, Chlorococcum sp., Chlorogonium, Chroomonas sp.,Chrysosphaera sp., Cricosphaera sp., Crypthecodinium cohnii, Cryptomonassp., Cyclotella cryptica, Cyclotella meneghiniana, Cyclotella sp.,Dunaliella sp., Dunaliella bardawil, Dunaliella bioculata, Dunaliellagranulate, Dunaliella maritime, Dunaliella minuta, Dunaliella parva,Dunaliella peircei, Dunaliella primolecta, Dunaliella salina, Dunaliellaterricola, Dunaliella tertiolecta, Dunaliella viridis, Dunaliellatertiolecta, Eremosphaera viridis, Eremosphaera sp., Ellipsoidon sp.,Euglena spp., Franceia sp., Fragilaria crotonensis, Fragilaria sp.,Gleocapsa sp., Gloeothamnion sp., Haematococcus pluvialis, Hymenomonassp., Isochrysis aff. galbana, Isochrysis galbana, Lepocinclis,Micractinium, Micractinium, Monoraphidium minutum, Monoraphidium sp.,Nannochloris sp., Nannochloropsis salina, Nannochloropsis sp., Naviculaacceptata, Navicula biskanterae, Navicula pseudotenelloides, Naviculapelliculosa, Navicula saprophila, Navicula sp., Nephrochloris sp.,Nephroselmis sp., Nitschia communis, Nitzschia alexandrina, Nitzschiaclosterium, Nitzschia communis, Nitzschia dissipata, Nitzschiafrustulum, Nitzschia hantzschiana, Nitzschia inconspicua, Nitzschiaintermedia, Nitzschia microcephala, Nitzschia pusilla, Nitzschia pusillaelliptica, Nitzschia pusilla monoensis, Nitzschia quadrangular,Nitzschia sp., Ochromonas sp., Oocystis parva, Oocystis pusilla,Oocystis sp., Oscillatoria limnetica, Oscillatoria sp., Oscillatoriasubbrevis, Parachlorella kessleri, Pascheria acidophila, Pavlova sp.,Phaeodactylum tricomutum, Phagus, Phormidium, Platymonas sp.,Pleurochrysis carterae, Pleurochrysis dentate, Pleurochrysis sp.,Prototheca wickerhamii, Prototheca stagnora, Prototheca portoricensis,Prototheca moriformis, Prototheca zopfii, Pseudochlorella aquatica,Pyramimonas sp., Pyrobotrys, Rhodococcus opacus, Sarcinoid chrysophyte,Scenedesmus armatus, Schizochytrium, Spirogyra, Spirulina platensis,Stichococcus sp., Synechococcus sp., Synechocystisf, Tagetes erecta,Tagetes patula, Tetraedron, Tetraselmis sp., Tetraselmis suecica,Thalassiosira weissflogii, and Viridiella fridericiana.

In some embodiments, the microorganisms are cultured autotrophically orphototrophically. In some embodiments, the microorganisms are culturedmixotrophically. In some embodiments, the microorganisms are culturedheterotrophically.

The concentration of the microorganisms in the aqueous suspension willdepend in part on the type of microorganism, size of the microorganism,maturity of the microorganism, cell wall characteristics of themicroorganism, contaminant load, the culture temperature, the culturepH, the culture salinity level, available nutrients and other variousparameters which may be modified or adjusted according to variousembodiments. In other embodiments, such parameters are dictated bynature or the natural environment and the available resources. In someembodiments, the aqueous slurry is cultured and used in the methods andsystems at any suitable concentration, such as, but not limited, to arange from about 100 mg/L to about 5 g/L (e.g., about 500 mg/L to about1 g/L).

According to some embodiments, the pH of the slurry during aggregationcan vary. In various embodiments, the pH is alkaline. However, in otherembodiments, acid or base can be added to keep the pH at a desired levelor measure, which can be kept in a range from 6-10.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a rectangular channel embodiment of an aggregation device.

FIG. 2A shows a rectangular channel embodiment of an aggregation devicewhere the height of the channel varies over the length of the channel.

FIG. 2B shows a rectangular channel embodiment of an aggregation devicewhere the width of the channel varies over the length of the channel.

FIG. 3A shows an embodiment with a channel formed by curvedsemi-circular electrodes separated by a pair of insulated spacers wherethe diameter of the channel varies over the length of the channel.

FIG. 3B shows an embodiment with a channel formed by curved electrodesseparated by a pair of insulated spacers where the height and width ofthe channel can vary over the length of the channel.

FIG. 4A shows an embodiment with a series of rectangular channelscoupled in a telescoping arrangement.

FIG. 4B shows a side view of an embodiment with a series of rectangularchannels coupled in a telescoping arrangement.

FIG. 4C shows an embodiment with a series of curved channels coupled ina telescoping arrangement.

FIG. 5A shows a tube-within-a-tube embodiment where the outer tube isconical and the inner tube has a constant diameter.

FIG. 5B shows cut-away view of the tube-within-a-tube embodiment wherethe outer tube is conical and the inner tube has a constant diameter.

FIG. 5C shows a tube-within-a-tube where the outer tube has a constantdiameter and the inner tube is conical.

FIG. 5D shows a cut-away view of the tube-within-a-tube where the outertube has a constant diameter and the inner tube is conical.

FIG. 6 shows an embodiment with an arrangement of electrodes within apipe or tube.

FIG. 7A shows a straight-on view of an embodiment of electrodes within apipe or tube.

FIG. 7B shows a side view of an embodiment of electrodes within a pipeor tube.

FIGS. 8A-C each show an embodiment with an arrangement of electrodeswithin a pipe or tube and various cross-sectional areas of electricalfields shown in dashed lines.

FIG. 9 shows an embodiment with an arrangement of electrodes within apipe or tube and a cross-sectional area of an electrical field shown indashed lines.

FIG. 10 shows an embodiment with an arrangement of electrodes within apipe or tube and a cross-sectional area of an electrical field shown indashed lines.

FIG. 11 shows an embodiment with an arrangement of electrodes within apipe or tube and a cross-sectional area of an electrical field shown indashed lines.

FIG. 12 shows an embodiment with an arrangement of electrodes within apipe or tube and a cross-sectional area of an electrical field shown indashed lines.

FIGS. 13A-C each show an embodiment with an arrangement of electrodeswithin a pipe or tube and various cross-sectional areas of electricalfields shown in dashed lines.

FIGS. 14A-C each show an embodiment with an arrangement of electrodeswithin a pipe or tube and various cross-sectional areas of electricalfields shown in dashed lines.

FIG. 15A shows a diagram of a system with multiple pulse generators andmultiple electrode sets.

FIG. 15B shows a diagram of a system with a programmable pulsegenerator.

FIG. 16 shows an exemplary embodiment of a disassembledtube-within-a-tube configuration.

FIG. 17 shows an exemplary embodiment of a disassembledtube-within-a-tube configuration.

FIGS. 18A-D each show exemplary embodiments of series systems, parallelsystems, and series/parallel systems with various electric and acousticdevices.

FIG. 19 shows an exemplary system where the suspension exiting theelectrical field may be recycled back into the apparatus for furthertreatment.

FIGS. 20A-B each show exemplary systems that combine electrical energyand acoustic energy.

FIG. 21 shows an exemplary embodiment that combines electrical andacoustic energy.

FIG. 22 shows an exemplary embodiment that combines electrical andacoustic energy.

DETAILED DESCRIPTION Rectangular Channel Embodiment

With reference to the Figures, the methods, systems and apparatusesdescribed generally will now be discussed in greater detail withreference to illustrative embodiments. According to various embodiments,some methods include providing an aggregation apparatus that includes,among other things, a channel or fluid path for flowing themicroorganisms through an electrical field that is sufficiently strongto aggregate the microorganisms without causing lysing or disruption ofthe microorganism cell walls or membranes. In some further embodiments,the apparatus includes an anode and a cathode that form a channelthrough which the aqueous slurry can flow. For example, FIG. 1illustrates a schematic of a portion of an aggregation device 100 thatis suitable for use in various methods according to some embodiments. Insuch embodiments, the illustrated portion of aggregation device 100includes a body 102 that comprises an anode 104 and a cathode 106electrically separated by an insulator 108. In various embodiments,anode 104 and cathode 106 are spaced apart to form a channel 112 thatdefines a fluid flow path 110. According to various embodiments, channel112 has a length 116 that extends the length of the anode and cathodeexposed to the fluid flow path 110. Likewise, in various embodiments,channel 112 also has a width 118 that is defined by the space betweenthe insulators 108 that is exposed to the anode 104 and cathode 106.Thus, as illustrated in FIG. 1, and according to some embodiments,channel 112 is bounded on its sides so as to form an opening and an exitthrough which fluid can be caused to flow (e.g., by pumping, gravity).In some embodiments, the spaced insulators are not used and instead theanode 104 and cathode 106 are disposed in an opposing arrangement withina housing.

According to some embodiments, as further illustrated in FIG. 1, the gapheight 114 between anode 104 and cathode 106 has a distance suitable forapplying an electrical field to the aqueous suspension. In at least oneembodiment, for example, gap 114 is in a range from 0.5 mm to 200 mm. Invarious embodiments, gap height 114 is in a range from 1 mm to 50 mmwhile in other embodiments gap height 114 is in a range from 2 mm to 20mm. In some embodiments, the narrow gap height 114 coupled with acomparatively large width 118 and length 116 can provide a large volumefor channel 112 while maintaining a strong electrical field foraggregating the microorganisms.

In some embodiments, width 118 of channel 112 can be any width so longas the materials of anode 104 and cathode 106 are sufficiently strong tospan the width without contacting one another and thus shorting thesystem or apparatus. In at least one embodiment, the volume of channel112 between anode 104 and cathode 106 and within gap distance 114,(i.e., the gap volume) is at least 50 ml. In other embodiments, however,the gap volume is at least 200 ml while in other embodiments the gapvolume is at least 500 ml. In yet additional embodiments, the gap volumeis at least 1 liter. In other embodiments, the gap volume exceeds 1liter. In additional embodiments, the surface area of anode 104 andcathode 106 exposed to fluid flow 110 (i.e. the gap surface area) is atleast 500 cm². In other embodiments, the gap surface area is at least1000 cm² while in other embodiments the gap surface area is at least2000 cm². In yet other embodiments, the gap surface area exceeds 2000cm².

Varying Channel Dimensions Embodiment

In some embodiments, the gap width 118 and/or the gap height 114 canvary over the length of the channel, as illustrated in FIGS. 2A and 2B.In some embodiments with a long flow path length, long residence time orrecirculation of the electrically treated aqueous suspension themicroorganisms may aggregate while within the channel flow path. A gapincreasing in width and/or height over the length allows for fewer clogsas the microorganisms aggregate over the length of the flow path, anddecreases the flow rate exiting the flow path 210. In other embodiments,a gap decreasing in width and/or height over the length creates a nozzleand an increase in the flow rate exiting the flow path 210. The desiredflow rate exiting the flow path may depend on the shear sensitivity ofaggregations of microorganisms that form within the flow path. Infurther embodiments, a gap varying in width and/or height over thelength with a consistent current supply will adjust the properties ofthe electrical field over the length of the channel by increasing ordecreasing the intensity without adjusting the amount of current used.

In the aggregation device 200, the change in the gap width 118 and/orthe gap height 114 over the length of the body 202 can be achievedthrough various means such as, but not limited to, the shape of theinsulators 208, the shape of the anode 204, the shape of the cathode206, or any combination thereof. In some embodiments, the height 220 ofat least one of the insulators 208 increases over the length 216 of thechannel 212. For example, as illustrated in FIG. 2A, gap height 220 isgreater than gap height 214. Conversely, in some embodiments, althoughnot shown, the height of the insulators 208 decreases over the length216 of the channel 212 so that gap height 220 is less than gap height214. In some embodiments, the width 218 of the cathode 206 increasesover the length of the channel 212. In some embodiments, the width 218of the cathode 206 decreases over the length of the channel. Forexample, as illustrated in FIG. 2B, gap width 222 is smaller than gapwidth 218. Conversely, in some embodiments, the gap width decreases overthe length of the channel. For example, in some embodiments, althoughnot shown, gap width 222 can be greater than gap width 218. In someembodiments, the width of the anode increases over the length of thechannel. In some embodiments, the width of the anode decreases over thelength of the channel. In some embodiments, the width and height of thechannel can both vary over the length of the channel.

In some embodiments, the channel is formed by a curved semi-circularanode and a curved semi-circular cathode separated by a pair ofinsulators, and has a circular cross-section. The circular cross-sectionmay have a diameter increasing or decreasing over the length of thechannel, similar to the height and width described above, to form aconical shaped channel. For example, in some embodiments, as shown inFIG. 3A, diameter 304 can be greater than diameter 302. Conversely, insome embodiments, although not shown, diameter 304 can be less thandiameter 302.

In other embodiments, the channel is formed by a curved anode and curvedcathode separated by a pair of insulator, and has a curved cross-sectionthat has a height and a width. Such an embodiment is illustrated in FIG.3B, which depicts width 306 and height 308. The height and width mayvary over the length of the channel, so that the curved cross-sectionvaries in size and shape over the length of the channel.

According to some embodiments, the length of the channel is thedimension commensurate with or in the direction of fluid flow (thelongitudinal direction) and can be any length so long as the channel isnot occluded by clogging (e.g., with the microorganism aqueoussuspension flowing there through) or hampered by significant pressuredrops which decrease the flow rate below a desired value. In at leastone embodiment, the length of the channel is at least 25 cm. In otherembodiments, however, the length is 50 cm, while in other embodimentsthe length is 100 cm. In still other embodiments, the length is at least200 cm, while in yet other embodiments the length exceeds 200 cm. Inadditional embodiments, the length can be less than 1000 cm, less than500 cm, or less than 250 cm.

Adjustable Channel Dimensions Embodiment

In some embodiments, the dimensions of the channel are fixed. In otherembodiments, the gap width, the gap height of the channel, and thelength of the channel are adjustable. An adjustable channel providesanother method of adjusting the electric field and flow rate withoutchanging the power source or pumps. An adjustable channel, such as atelescoping configuration, also allows the apparatus to adjust in sizeto be retro fit into fixed spaces and allows for easier transportationwhen collapsed.

In some embodiments, the channel comprises a series of channels coupledin a telescoping manner as illustrated in FIG. 4A. In a telescopingarrangement the channel may be uniform when collapsed, and may have adecreasing height and width or an increasing height and width when thelength is extended. For example, as shown in FIG. 4B, when a telescopingembodiment is extended over length 402, the height of the series ofchannels can decrease over length 402 so that height 408 is greater thanheight 406 which is greater than height 404. The telescopingconfiguration can also be arranged so that that the algal suspensionflows in the opposite direction than as illustrated in FIG. 4B, i.e., sothat the height of the series of channels increases over length 402. Thenested channels of a telescoping arrangement may be constructed asdescribed above with an anode, cathode, and insulators forming theboundaries of the channel.

In addition to the embodiments having telescoping rectangular channelsshown in FIGS. 4A and 4B, other telescoping embodiments have a series ofchannels formed by curved semi-circular anodes and curved semi-circularcathodes separated by a pair of insulators, as illustrated in FIG. 4C.In such embodiments, the series of channels can be arranged so that thediameter of the extended channel increases or decreases over the lengthof the extended telescoping configuration.

Adjustable Electrode within a Tube Embodiment

In another embodiment, the channel may be defined by an outer conductivetube forming a first electrode and a second electrode positioned withinthe inner void of the outer conductive tube. In some embodiments, theelectrodes comprise a “tube within a tube” electrode arrangement of anyshaped tubes, such as, but not limited, to circular tubes or polygontubes. In some embodiments, the inner electrode is placed concentricallywithin the outer electrode. In some embodiments, the inner electrode isa solid rod. In some embodiments, the inner electrode is planar. In someembodiments, the outer conductive tube comprises a series of spaced ringelectrodes. In some embodiments, the inner and outer electrodes aredifferent shapes.

In some embodiments, as shown in FIG. 5A, the outer conical electrodecan have an increasing diameter over length 504 so that 506 (exit flowdiameter) is greater than 502 (inflow diameter). In this embodiment, theinner electrode is tubular with a constant diameter, as shown in FIG.5B. Conversely, in another embodiment, fluid can flow in the oppositedirection so that the channel has a decreasing diameter over length 504of the channel. In another embodiment, as shown in FIG. 5C, the outerelectrode is tubular with a constant diameter and the inner electrode isconical with a diameter that increases over length 510 so that exit flowdiameter 512 is greater than inflow diameter 508. The conical shape ofthe inner electrode is shown in FIG. 5D. Conversely, in anotherembodiment, the fluid can flow in the opposite direction so that thatthe diameter of the inner conical electrode decreases over length 510.

In some embodiments, the outer and inner electrodes comprise a series ofchannels coupled in a telescoping manner, as described above. In someembodiments, the telescoping outer and inner electrodes have anasymmetrical number of telescoping sections or thicknesses, whichresults in a change in the channel cross-sectional area when extended.

Electrodes

According to various embodiments, the anode and cathode can be made ofany electrically conductive material suitable for applying an electricalfield across the various gaps described herein, including but notlimited to metals such as, but not limited to, steel, aluminum, copper,nickel, titanium and conductive composites or polymers, such asgraphite. In some embodiments, the material selected for the anode andcathode are resistant to corrosion, while in other embodiments thematerial selected is non-corrosive or damage stabilized. In someembodiments, the electrically conductive material may be coated bymaterials comprising iridium, ruthenium, platinum, rhodium, tantalum,and mixed metal polymers. The electrode material and coating may beselected to minimize the amount of pitting on the electrode and/or theamount of the electrode conductive material or coating which leachesinto the aqueous suspension during operation.

In various embodiments, the shape of the anode and cathode can beplanar, cylindrical or any other suitable solid, hollow, wire, mesh orperforated shape(s). According to at least some embodiments, asdescribed more fully below, an annulus created between an innerconductive (and in some embodiments metallic) surface of a larger tubeand an outer surface of a smaller conductive tube (also metallicaccording to some embodiments) placed within the larger tube is suitablefor its ability to avoid fouling and/or shorting and to maintain a highsurface area in a compact design. However, the tubes need not have acircular periphery as an inner or outer tube may be square, rectangular,polygonal, or any other suitable shape according to various embodiments.Moreover, the tube shape does not necessarily have to be the same,thereby permitting tube shapes of the inner and outer tubes to bedifferent in some embodiments. In at least one embodiment, the inner(smaller) conductive tube and outer (larger) conductive tube areconcentric tubes, with at least one tube, preferably the outer tube,being provided with a plurality of spiral grooves separated by lands toimpart a rifling to the tube. This rifling, according to someembodiments, has been found to decrease build-up of residue on the tubesurfaces. In some commercial embodiments, there may be a plurality ofinner tubes surrounded by an outer tube to increase the surface contactof the conductors with the microorganisms or to otherwise increase theresidence time and/or concentration of electrical current applied to themicroorganisms. In some embodiments, the electrodes may comprise wireelectrode wrapped in a coil configuration. Either the anode and/or thecathode may be spiral shaped or form one or more rings in the conduitcontaining the liquid flow.

In other embodiments, however, the use of electrical insulators, such asplastic tubes, baffles, and other devices, can be used to separate alarge aggregation device into a plurality of zones, so as to efficientlyscale-up the invention for commercial applications.

In performing the method according to certain embodiments, the aqueoussuspension containing microorganisms is fed through a channel alongfluid flow path between the anode and cathode (i.e., through the gap).According to certain embodiments, power is applied to the anode andcathode to produce an electrical field that aggregates themicroorganisms by affecting the surface charge and without causing thecells to be compromised, lysed or disrupted. In various embodiments, thecharacteristics of the electrical field depend on the composition of theaqueous suspension, the gap dimensions, the electrode materials, thecharacteristics of the electrical current, and the flow rate.

The apparatus comprises an aqueous suspension disposed between thecathode and anode. According to some embodiments, the aqueous suspensioncontaining microorganisms is caused to flow through the channel using apump or gravity. In such embodiments, and by way of an electricalconduit, a negative connection is made to the anode, which provideselectrical grounding. Further according to such embodiments, a positiveelectrical input is also delivered by way of a conduit connection inorder to provide a positive electrical transfer throughout the cathode.According to such embodiments, when a positive current is applied to thecathode, the positive current then seeks a grounding circuit forelectrical transfer, or in this case, to the anode, which allows thecompletion of an electrical circuit. In this respect, and according tosuch embodiments, an electrical field is created through a transfer ofelectrons between the positive and negative surfaces areas, but onlywhen an electrically conductive liquid is present between them. Thus,according to such embodiments, as the liquid medium containing theaqueous suspension is flowed between the surface areas, an electricaltransfer from the cathode through slurry to the anode occurs. In otherwords, as an aqueous suspension containing microorganisms transversesthe anode and cathode circuit according to the embodiments describedabove, the microorganism cells are exposed to an electric field thatcauses aggregation of the cells or otherwise induces the cells tosubsequently aggregate following exposure to the electric field.

A simplified description to illustrate an electrical transfer betweentwo electrical conductive components with a liquid medium containing aliving microorganism biomass flowing between them is described below.According to some embodiments, the cathode uses a positive electricalconnection point, which is used for positive current input according tosome embodiments. According to such embodiments, positive transferpolarizes the entire length and width of the cathode and seeks agrounding source in the anode. In order to complete an electricalcircuit, according to such embodiments, the anode includes a groundingconnection point, which allows an electrical transfer to occur throughaqueous slurry according to some embodiments. In some embodiments, theaqueous slurry includes a liquid medium that contains a nutrient sourcemainly composed of a conductive mineral content that was used during agrowth phase of the microorganism in the aqueous slurry. According tosuch embodiments, the liquid medium containing the nutrient sourcefurther allows positive electrical input to transfer between the cathodethrough the liquid medium/biomass to the anode, which, according to someembodiments, only occurs when the liquid medium is present or flowing.Additionally, in some embodiments, the amount of electrical voltageand/or current or frequency input can be adjusted based on a matrixformula of grams of microorganism biomass contained in 1 liter of theliquid medium.

Tunable Electrical Field

In some embodiments, the electrodes within a pipe or tube comprise anarrangement in which the electrodes are capable of changing thecross-sectional shape and area of the electric field within the flowpath of the channel, as shown in FIG. 6. In some embodiments, theelectrodes comprise at least one cathode 613, at least one anode 609, atleast one collector electrode 611, and at least one control electrode615. The at least one cathode 613 may be solid or hollow. The at leastone cathode 613 may be a rod, plate or tube. The at least one cathode613 may have a circular, oval or polygonal shaped cross-section. The atleast one anode 609 may have a semi-circular cross section or a circularcross section. The at least one collector electrode 611 may have acircular, oval, polygonal, curved or v-shaped cross-section. The atleast one control electrode 615 may have a circular, oval or polygonalshaped cross-section.

In a configuration with at least one cathode, at least one anode, atleast one collector electrode, and at least one control electrode, thecurrent leaving the at least one cathode is simultaneously subjected totwo electrostatic fields. One field being positive and the other fieldbeing negative. The negative field cooperates with the positive field tocompress the current flow of the electrical field, with the ratiobetween the positive field and negative field controlling how far theelectrical field cross-sectional area expands or contracts. Inoperation, the at least one collector electrode and the at least oneanode are maintained at a positive potential with respect to the atleast one cathode. The positive potential of the at least one anode islarger than the potential of the at least one collector electrode. Theat least one control electrode is maintained at a negative potentialwith respect to the at least one cathode.

The ratio between the positive field and the negative field may bechanged by increasing or decreasing the potential of the at least onecollector electrode and/or the at least one control electrode, thusaffecting the cross-sectional area of the electrical field. With theability to increase or decrease the cross-sectional area of theelectrical field, the electrical field can be focused to a desired sizeor a desired location within the flow path channel. This allows for amore focused and finely tuned application of electricity to the algaesuspension, which in turn allows for better manipulation and control ofthe algal flow. Decreasing the negative potential of the at least onecontrol electrode allows the current flow from the at least one cathodeto the central portion of the at least one collector electrode, or tothe edge of the at least one collector electrode, or beyond the at leastone collector electrode to the at least one anode. In a similar manner,the cross-sectional area of the current flow from the at least onecathode to the at least one anode can be contracted by increasing thenegative potential of the at least one control electrode.

Increasing the positive potential of the at least one collectorelectrode can also expand the cross-sectional area of current flowingfrom the at least one cathode to a larger surface area of the at leastone collector electrode. Decreasing the positive potential of the atleast one collector electrode can also contract the cross-sectional areacurrent flowing from the at least one cathode to a smaller surface areaof the at least one collector electrode. Decreasing the positivepotential of the at least one collector electrode when the negativepotential of the at least one control electrode is also decreased willexpand the cross-sectional area of the current flow from the at leastone cathode to the at least one anode, and decrease the current flowfrom the at least one cathode to the at least one collector electrode.In a similar manner, increasing the positive potential of the at leastone collector electrode when the negative potential of the at least onecontrol electrode is decreased will contract the cross-sectional area ofthe current flow from the at least one cathode to the at least oneanode, and expand the cross-sectional area of the current flow from theat least one cathode to the at least one collector electrode.

In one exemplary embodiment, as shown in FIGS. 7A-B and 8A-C, two curvedplate anodes 709 are disposed opposite each and on the inner surface ofa tube or pipe shaped housing 701 in FIGS. 7A-B. The tube or pipe shapedhousing 701 may be made from a non-conductive material. Disposed betweenthe two anodes 709 are a vertical pair of parallel plate collectorelectrodes 711. A circular cross-section shaped rod cathode 713 iscentered between the anodes 709 and the collector electrodes 711. Twocircular rod shaped control electrodes 715 are disposed on each side ofthe cathode 713 between the cathode 713 and one of the anodes 709. Insome embodiments, the anodes 709 may be electrically independent of eachother and supplied current by individual connections. A flow path for anaqueous suspension is provided between the interior surface of the tubeor pipe shaped housing and the exterior surfaces of the variouselectrodes.

As shown in FIG. 8A-C, the potential applied to the collector electrodes811 and/or the control electrodes 815 can manipulate the cross-sectionalarea of the electrical field. In a balanced condition, the controlelectrodes 815 may be biased negatively to an extent sufficient tocompel the current leaving the cathode 813 to travel to the collectorelectrodes 811 and not reach the anodes 809. For the balanced conditionneither a high positive potential of the collector electrodes 811 nor ahigh negative potential on the control electrodes 815 is necessary. Asthe collector electrodes 811 are made more positive or the controlelectrodes 815 are made more negative than the balanced condition, thecross-sectional area of the electrical field expands out towards theedge of the collector electrodes 811. A decrease in the positivepotential applied to the collector electrodes 811 or a further decreasein the negative potential applied to the control electrodes 815 resultsin the cross-sectional area of the electrical field expanding beyond thesurface of the collector electrodes 811 to the anodes 809. Similarly,manipulating the collector electrodes 811 and control electrodes 815 inan opposite manner will contract the cross-sectional area of theelectrical field. Variations in the electrical field are expressed asdashed lines in the FIGS.

In other embodiments illustrated by FIGS. 9 and 10, the anode 909, 1009comprises a round, conductive tube or a series of conductive rings, andthe cathode 913, 1013 is a circular rod disposed concentrically withinthe anode 909, 1009. The anode 909, 1009 may be disposed within atubular housing or piping 901, 1001. The collector electrodes 911, 1011comprise four rods 911 or plates 1011 disposed with even spacing aroundthe cathode 913, 1013, and between the anode 909, 1009 and the cathode913, 1013. The control electrodes 915, 1015 comprise four rods disposedwith even spacing around the cathode 913, 1013, and between the anode909, 1009 and the cathode 913, 1013. A flow path for an aqueoussuspension is provided between the inner surface of the anode 909, 1009and the exterior surfaces of the other electrodes. When the potentialapplied to the collector electrodes 911, 1011 and the control electrodes915, 1015 is manipulated as previously described above the currentflowing from the cathode 913, 1013 extends to the collector electrodes911, 1011 and beyond to the anode 909, 1009 in a plurality of bandsequal to the number of collector electrodes. The number of collectorelectrodes and control electrodes are equal, and the number ofelectrodes is limited only by the physical dimensions of the electrodesand space available within the tubular anode.

In another exemplary embodiment illustrated by FIG. 11, the anode 1109comprises two curved plates disposed opposite each other and within theinner surface of a tube or pipe 1101. The cathode 1113 comprises acircular cross-section shaped rod centered between the anodes 1109. Thecollector electrodes 1111 comprise a vertical pair of plates with av-shaped cross-section disposed between the anodes 1109 and on opposingsides of the cathode 1113. The two control electrodes 1115 plates aredisposed on each side of the cathode 1113 between the cathode 1113 andone of the anodes 1109. A flow path for an aqueous suspension isprovided between the inner surface of the anode 1109 and the exteriorsurfaces of the other electrodes. When the potential applied to thecollector electrodes 1111 and the control electrodes 1115 is manipulatedas previously described above, the cross-sectional area of theelectrical field is changed.

In another exemplary embodiment as shown by FIG. 12, the anode 1209comprises a single curved plate. The collector electrode 1211 comprisesa plate with a v-shaped cross-section disposed opposite the anode 1209.The cathode 1213 comprises a circular cross-section shaped rod centeredbetween the anode 1209 and the collector electrode 1211. The controlelectrode 1215 comprises a flat plate disposed between the cathode 1213and the anode 1209. A flow path for an aqueous suspension is providedwithin a tube or pipe shaped housing which houses the electrodes, andparticularly between the anode 1209 and collector electrode 1211. Whenthe potential applied to the collector electrodes 1211 and the controlelectrodes 1215 is manipulated as previously described above, thecross-sectional area of the electrical field is changed.

In another exemplary embodiment shown in FIGS. 13A-C, the anode 1309comprises a round, conductive tube or series of conductive rings, andthe cathode 1313 is a square rod disposed concentrically within theanode 1309. The collector electrodes 1311 comprise a pair of flat platesdisposed on opposite sides of the cathode 1313. The control electrodes1315 comprise a pair of flat plates disposed on opposite sides of thecathode. A flow path for an aqueous suspension is provided between theinterior surface of the anode 1309 and the exterior surfaces of theother electrodes. The entire set is located inside a non-conductivetubular housing 1301. When the potential applied to the collectorelectrodes 1311 and the control electrodes 1315 is manipulated aspreviously described above, the cross-sectional area of the electricalfield is changed.

In another exemplary embodiment illustrated by FIG. 14A-C, anode 1409comprises two curved plates disposed opposite each other. Cathode 1413comprises a circular cross-section shaped electrode centered betweenanodes 1409. Collector electrodes 1411 comprise a vertical pair ofplates spaced evenly around cathode 1413 and between anodes 1409 andcathode 1413. Two control electrodes 1414 are disposed on each side ofcathode 1413 between cathode 1413 and one of anodes 1409. A flow pathfor an aqueous suspension is provided between the interior surface ofthe anode 1409 and the exterior surfaces of the other electrodes. Whenthe potential applied to the collector electrodes 1411 and the controlelectrodes 1415 is manipulated as previously described above, thecross-sectional area of the electrical field is changed.

In some embodiments, as mentioned above, the foregoing electricaltransfer through the living microorganism is achievable due to nutrientscontaining electrically conductive minerals suspended within the aqueoussuspension or the salinity level of the aqueous suspension.

In at least one embodiment, the flow rate through the gap volume (i.e.,the portion of channel 112 in the electric field at the gap distance114) is 0.1 ml/second per ml of gap volume. In other embodiments,however, the flow rate through the gap volume is at least 0.5 ml/secondper ml of gap volume while in other embodiments the flow rate throughthe gap volume is at least 1.0 ml/second per ml of gap volume. In stillother embodiments, the flow rate through the gap volume is at least 1.5ml/second per ml of gap volume. In yet other embodiments, the flow ratethrough the gap volume exceeds 1.5 ml/second per ml of gap volume. In atleast one additional embodiment, the flow rate can be controlled bycontrolling the pressure using a pump or other suitable fluid flowmechanical devices. In other embodiments, the flow rate is affected bythe varying dimensions of the flow path channel.

Characteristics of Electrical Power

In some embodiments, the electrical field is sustained at a constant orcontinuous level with direct current. In some embodiments, theelectrical field is varied by using an alternating current or can bepulsed on and off repeatedly. Whether the electrical field iscontinuous, varying, or pulsed, the amplitude and/or intensity of theelectrical field is selected to induce aggregation of the microorganismswithin the aqueous suspension without lysing or disrupting the cellmembrane of the microorganisms. According to such embodiments, voltagescan be higher and peak amperage lower while average amperage remainsrelatively low. In such embodiments, this condition or controlledcircumstance reduces the energy requirements for operating the apparatusand reduces wear on the anode and cathode pair or pairs. In someembodiments, the frequency of the electrical field pulse is at leastabout 500 Hz, 1 kHz, 2 kHz, 30 kHz, 50, kHz, 80, kHz, or 200 kHz. Insome embodiments, the electrical pulse duration ranges from 1 nanosecondto 100,000 nanoseconds, 1 to 1,000 nanoseconds, 1 to 500 nanoseconds, or10 to 300 nanoseconds; allowing for frequencies of about 10 kHz to1,000,000 kHz. Ranges for the pulse frequency can be any combination ofthe foregoing maximum and minimum frequencies according to variousembodiments. In some embodiments, the use of nanosecond pulses reducesthe thermal effects on the aqueous suspension and the production ofexcess free charges in the aqueous slurry, which may limit the galvanicprocesses that lead to corrosion, pitting, and leaching of electrodemetals. In some embodiments, the use of a pulsed electrical fieldreduces the overall power requirements of the apparatus, system and/ormethod, compared to the use of a constant or continuous electricalfield.

In some embodiments, the electrical pulses are provided by a pulsegenerator. In some embodiments, the pulse shape is rectangular,trapezoidal, exponentially decaying, unipolar or bipolar. In furtherembodiments, the pulse generator produces two different pulse types. Instill further embodiments, the pulse generator produces at least twodifferent pulse types. In some embodiments, the pulses are provided in acontinuous manner and each pulse is identical in pulse amplitude, pulseduration, pulse shape, and pause duration between pulses. In someembodiments, the pulses are provided in continuous manner and at leastone of the pulse amplitude, pulse duration, pulse shape, and pauseduration between pulses varies. In further embodiments, the pulseamplitude and duration are identical in each pulse, but the duration ofthe pause between pulses varies. In further embodiments, the pulsesalternate between two different pulses in a pattern, such as but notlimited to long pulse then short pulse. In further embodiments, thepattern of pulses repeat a pattern more complex than simply alternatingbetween two pulse types (similar to a Morse code transmission), such asbut not limited to short pulse, short pulse, long pulse, short pulse,long pulse, long pulse. In further embodiments, the pattern of pulsescomprises more than two pulse types. In some embodiments, multiple pulsegenerators and multiple electrode sets are used, as shown in FIG. 15A.In further embodiments, the varying pulse patterns are programmable intothe pulse generator. FIG. 15B shows an exemplary scheme of an apparatusthat includes a programmable pulse generator. In still furtherembodiments, the pulse pattern program utilized by the pulse generatoris selected by a computerized controller based on sensory input such as,but not limited to, turbidity of the aqueous suspension, density of theaqueous suspension, composition of the aqueous suspension, and flowrate.

In some embodiments, the power supply provides alternating current whilein other embodiments the power supply provides direct current. Moreover,in some embodiments, the anode and the cathode pair are fixed duringaggregation while in other embodiments the anode/cathode pair or circuitalternates during aggregation.

In various embodiments, the average amperage is at least 1 amp, 5 amps,10 amps, 50 amps, or even at least 100 amps. According to at least someembodiments, the maximum amps can be less than 200 amps, less than 100amps, less than 50 amps, or less than 10 amps. As with pulse frequencyand the like, the range of amperage can be any range from the foregoingmaximum and minimum amperages according to various embodiments. Thecurrent density (amps/cm²) is defined as the flow of the electric chargeper surface area of the electrodes. The current level and dimensions ofthe electrode may be selected together in a manner to optimize thecurrent density, which is a factor in the pitting and/or leaching of theelectrode metals.

Similarly, according to various embodiments, the voltage can be at least1V, 10V, 100V, 1 kV, 20 kV, 50 kV, 100 kV, or 500 kV. Again, the rangeof voltage can be any range of the foregoing maximum and minimumvoltages according to various embodiments. The voltage of the electricalfield may be selected in conjunction with the gap distance of the flowpath to produce an optimal electrical field for aggregatingmicroorganisms without lysing or disrupting the cell membranes. In someembodiments, the amplitude (the applied voltage divided by distancebetween electrodes) of the electrical fields to which the aqueous slurryis exposed to may range from 0.05 V/cm to 1,000 kV/cm. In someembodiments, the amplitudes of the electrical fields to which theaqueous slurry is exposed to may range from 0.1 to 100,000 kV/cm, 10 to1,000 kV/com, 50 to 500 kV/cm, or 100 to 400 kV/cm.

The peak power of the electrical field may be at least 500 kW, or atleast 1 megawatt. The energy delivered by the electrical field may rangefrom 0.1 to 100 joules, or 1 to 10 joules. Depending on the compositionof the aqueous slurry, residence time, configuration of the electrodes,and configuration of the flow path channel, electrical field may betuned to induce aggregation of the microorganisms in 1-60 seconds, lessthan 5 minutes, less than 15 minutes, less than minutes, or less thanone hour.

Additional Details on Tube within a Tube Embodiment

As illustrated in FIG. 16, apparatus 1622 is comprised of a “tube withina tube” configuration according to some embodiments. According to someembodiments, FIG. 16 illustrates a disassembled aggregation deviceshowing a first (smaller) conductive tube 1603 (hereinafter cathode1603, although conductive tube 1603 may also be the anode or switchbetween anode and cathode according to various embodiments) that isconfigured to be placed in a second (larger) conductive tube 1602(hereinafter anode 1602, although conductive tube 1602 may also be thecathode or switch between anode and cathode according to variousembodiments). In some embodiments, the outer anode tube 1602 includes apair of containment sealing end caps 1607 and 1608. In such embodiments,sealing end cap 1607 provides an entry point 1609 used to accept anaqueous suspension. Following the transition of the aqueous suspensionthrough anode 1602 according to various embodiments, the opposing endcap 1608 provides an exit point 1610 to the outward flowing aqueoussuspension.

With continued reference to FIG. 16, in some embodiments, the innercathode tube 1603 includes sealed end caps 1611 and 1612 to preventliquid flow through the center of the tube and to divert the flowbetween the inner surface of anode 1602 and the outer surface of cathode1603, thereby forming a channel or annulus between anode 1602 andcathode 1603. In some embodiments, the channel can be sized andconfigured as described above. According to the foregoing embodiments,the use of a “tube within a tube” configuration is particularlyadvantageous for avoiding fouling or shorting by the microorganisms inthe aqueous suspension.

Turning now to FIG. 17, an alternative embodiment of apparatus 1722 isillustrated. As seen in FIG. 17, in some embodiments, an insulativespacer 1716 is positioned in the channel between anode 1702 and cathode1703 to cause spiraling fluid flow. In such embodiments, insulativespiraling isolator spacer 1716 serves as a liquid seal between the twowall surfaces 1714 and 1715 with the thickness of the spacer preferablyproviding equal distance spacing between anode 1702 and cathode 1703.According to some embodiments, the spacing and directional flow cancause the fluid flow path to complete a three hundred and sixty degreetransfer of electrical current around anode 1702 and cathode tube 1703.In some further embodiments, the spacer 1716 can also help preventcontact between anode 1702 and cathode 1703, which prevents shorting orfouling the anode and cathode pair and forces electrical current throughthe liquid medium. According to various embodiments, the spiralingisolator 1716 also provides a gap 1713 between the two wall surfaces1714 and 1715 allowing a passage way for a flowing aqueous suspension1701. In some embodiments, the spiraling directional flow furtherprovides a longer transit duration or residence time, which in turnprovides greater electrical exposure to the flowing aqueous suspension1701 thus increasing aggregation efficiency at a lower per kilowatt hourconsumption rate. In some embodiments, the width of the gap 1713 isuniform over the length of the passage way. In some embodiments, thewidth of the gap 1713 increases or decreases over the length of thepassage way. According to various embodiments, any suitable material canbe used as a spacer. According to some embodiments, ceramic, polymeric,vinyl, PVC plastics, bio-plastics, vinyl, monofilament, vinyl rubber,synthetic rubber, or other non-conductive materials are used.

Multiple Path Embodiments

A plurality of anode and cathode circuits, according to someembodiments, are configured in parallel having a common upper manifoldchamber, which receives an in flowing biomass a through entry port.According to such embodiments, once entering into the upper manifoldchamber, the biomass a makes a downward connection into each individualanode and cathode circuit through entry ports, which allow a flowingconnection, or a fluid connection, to the sealing end caps. According tosuch embodiments, it is at this point where the flowing biomass (i.e.,the aqueous suspension of microorganisms) enters into the anode andcathode circuits. Further according to such embodiments, once transitingthrough the individual circuits, which in some embodiments comprise aspiral flow path while in other embodiments a straight or otherconfigured fluid flow path is contemplated, the flowing biomass exitsinto a lower manifold chamber where the biomass is then directed to flowout of the apparatus (system) through an exit point.

As described herein, the flow path of each anode and cathode circuit mayhave different characteristics, such as but not limited to, height,width, diameter, length, electrode material, electrical fieldamplitude/intensity, electrical field cross section, and electricalpulse frequency/duration. Depending on the end use of the apparatusoutput, such as but not limited to fuel, food, feed, fertilizer,cosmetics and pharmaceuticals, the degree of aggregation and/or theelectrode material requirements may be different. For example, if theresulting aggregated microorganisms being sold as whole algae mayrequire different processing and ending solids percent than aggregatedmicroorganisms that will go through further downstream processing, suchas an extraction process. In some embodiments, the electrode materialsmay have a different effect on the microorganisms, therefore requiringmicroorganisms for specific products to be aggregated with electrodes ofa specific material. In some embodiments, the differently configuredflow paths with parallel anode and cathode circuits would allow theaqueous suspension to be split into separate streams for concurrentprocessing for different outputs. The differently processed streams mayexit the anode and cathode circuits into different separation tanks tomaintain segregation before going on to further processing. In otherembodiments, the plurality of anode and cathode circuits withdifferently configured flow paths may be connected in series, allowingthe aqueous suspension to go from one anode and cathode circuit to thenext in a series of varying conditions without adjusting the equipment.Embodiments of the various configurations are illustrated in FIGS.18A-D. Each different EA (electro apparatus) designates a differentelectric aggregating device. Any of the representative aggregatingsystems described in this specification can be used as a particular EAshown in the FIGS. 18A-D.

In some embodiments, the plurality of anode and cathode circuitscomprise the same configuration and are connected in series to increasethe residence time of the aqueous suspension within the electricalfield. In further embodiments, the apparatus may switch between aparallel connection configuration and a series connection configuration.In some embodiments, the plurality of anode and cathode circuits are allconnected in parallel or all connected in series. In some embodiments,the plurality of anode and cathode circuits are connected in acombination of parallel and series configurations. Non-limiting examplesof such embodiments with a combination of series and parallelconnections include: a plurality of groups of circuits connected inparallel wherein each group of circuits consists of at least twocircuits connected in a series; half of the circuits connected inparallel and the other half of the circuits connected in a series; and aplurality of groups of circuits connected in series wherein each groupof circuit consists of at least two circuits connected in parallel.

According to some embodiments, the various system embodiments discussedabove are adjustable, and can be set up with various flow rates,voltage, amperage, electrical pulse frequency/duration, electrical fieldamplitude/intensity, flow path width, flow path height, flow pathdiameter, flow path length and/or variable temperatures. According tosome embodiments, the microorganisms in suspension, enter into anelectrical field and are subjected to a current input for a prescribedtransit or residence time within the system (which can be adjustedaccording to flow rate, the use of spiraled or rifled circuits, or flowpath dimensions) which dictates the degree to which the microorganismsare aggregated. According to some embodiments, various determiningfactors for this method include, but are not limited to:

The amount of energy input (total wattage as a combination of volts andamps);

The frequency in which the electrical input is applied, and duration inwhich the electrical input is applied;

The type of electrical input applied, such as direct current,alternating current or electrical pulses;

The flow path length (e.g., a rifled interior circuit can have closerrifle spacing for a longer residence or duration flow or electricalfield exposure time, a larger rifle spacing for a shorter duration flowor electrical field exposure time, or a telescoping arrangement that canextend and contract in length);

The electrodes can have a smaller gap for longer duration or electricalfield exposure time or field strength, or a larger gap for a shorterduration flow or electrical field exposure time or field strength;

The electrode materials, such as steel, aluminum, copper, titanium,nickel, graphite, or conductive polymers, and any coatings on theelectrode materials;

A combination of the closer/larger rifle spacing, with a larger/smallerelectrode gap;

The concentration of the microorganism culture; and/or

The pH and the salinity of the culture.

According to various embodiments, the longer the total transit orresidence time, which can be determined by an adjustable flow rate orflow path dimensions, in combination with higher electrical input,provides greater electrical field exposure to the aqueous suspension. Insome embodiments, when setting lower electrical input and higher flowrate parameters, provides a lesser electrical field exposure.

In some embodiments, the use of electrical fields is used to aggregatethe microorganisms of an aqueous suspension. For example, microorganismsare grown in a liquid medium. According to some embodiments, themicroorganisms are grown in a growth chamber. In some embodiments, agrowth chamber may comprise or be comprised of a reactor, aphotobioreactor, a pond, or a fermenter. In other embodiments, themicroorganisms may be grown in a natural or outdoor environment. Forexample, according to some embodiments, the growth chamber can be anybody of water or container or vessel in which all requirements forsustaining life of the microorganisms are provided. Examples of growthchambers include, but are not limited to, an open pond, a trough, atube, a bag, or an enclosed growth tank. When added to the aggregationdevice, the microorganisms are generally in the form of a live slurry(also referred to herein as “biomass”) according to certain embodiments.In some embodiments, the live slurry is an aqueous suspension thatincludes microorganisms, water and nutrients such as an algal cultureformula comprising Guillard's 1975 F/2 algae food formula (0.82% Iron,0.034% Manganese, 0.002% Cobalt, 0.0037% Zinc, 0.0017% Copper, 0.0009%Molybdate, 9.33% Nitrogen, 2.0% Phosphate, 0.07% Vitamin B1, 0.0002%Vitamin B12, and 0.0002% Biotin) or a variation thereof, that providesnitrogen, vitamins and essential trace minerals for improved growthrates in freshwater and marine microorganisms. In various embodiments,any suitable concentration of microorganisms and sodium chloride, fresh,brackish or wastewater can be used, such that the microorganisms grow inthe aqueous suspension.

According to some embodiments, the microorganisms may be harvested bydrawing the aqueous microorganism slurry from the growth chamber usingvarious techniques. In at least one embodiment, the method ofaggregating microorganisms can be carried out by periodically drawingmicroorganisms from a growth chamber in a manner that maintains a steadyrate of growth. In such embodiments, steady state growth can be achievedby drawing microorganisms at a rate of less than half the microorganismmass per unit time that it takes for the microorganism to double. In oneembodiment, microorganisms are harvested at least as often as thedoubling time of the microorganism. In other embodiments, however, themicroorganism are harvested at least twice during the doubling time ofthe microorganism. In various embodiments, the doubling time will dependon the microorganism type and growth conditions but can be as little as6 hours to several days.

The method continues, according to some embodiments, through the use ofcavitation. For example, according to such embodiments, prior toaggregation, the slurry can optionally be processed using cavitationand/or heating. As the method continues, the slurry is then aggregatedusing an electrical field as described herein and according to variousembodiments disclosed herein.

In some embodiments, the aqueous slurry is then delivered to theaggregating apparatus using any means, such as, but not limited to,gravity or a liquid pump. As the method continues according to variousembodiments, the aqueous microorganism slurry is flowed via a conduitinto an inlet section of an anode and cathode circuit of an aggregationdevice using any suitable device or apparatus, e.g., pipes, canals, orother conventional water moving apparatus(es). In some embodiments, agrowth chamber or reactor is operably connected to the aggregatingapparatus such that the microorganisms within the growth chamber orreactor can be transferred to the apparatus as discussed above.

According to some embodiments, after the microorganisms are aggregated,the aggregated slurry is dewatered. In such embodiments, dewatering iscarried out by separating a portion of the aqueous medium from theaggregated microorganisms using various techniques. In one embodiment,for example, the treated, aggregated microorganisms can be harvestedfrom the top of the tank such as by skimming or passing over a weir,where they can be recovered and/or further processed. In suchembodiments, the aggregated microorganisms can float to the surface bycreating a bubble stream, either by cavitation of the creation ofmicrobubbles from a microbubble generator or fluidic oscillator, andimpinging the bubbles beneath the aggregated microorganisms to causethem to rise to the surface in a froth. Further according to suchembodiments, a skimming device is then used to harvest the frothfloating on the surface of the liquid column. The remaining liquid(e.g., water) can be filtered and returned to the growth chamber(recycled) or removed from the system (discarded) according to variousembodiments. In an alternative embodiment, the aggregated microorganismsmay be denser than the liquid medium and allowed to sink to the bottomof a settling tank. In such embodiments, the aggregated microorganismscan be collected in a gravity settling tank and the clarified water canbe recycled. In some embodiments, the aggregated microorganisms areseparated by a foam fractionation device. The foam fractionation devicereceives the aqueous suspension containing aggregated microorganisms,and creates a gas/liquid mixture in a liquid chamber by injecting a gasand producing bubbles/microbubbles. The bubbles/microbubbles causeaggregated particles of a threshold size to float to the surface of theliquid chamber and form a foam which may be collected. Any otherconventional technique for removing particles, such as filtering,settling, flocculation, centrifugation or other particle aggregationtechnique may be used, either before or after, in conjunction with thetechniques of the present invention.

Multiple Pass Embodiments

In some embodiments, at least a portion of the aqueous suspensionexiting the electrical field may be recycled for further exposure to theelectrical field for aggregation. Such a system is illustrated in FIG.19. A system with multiple passes of at least a portion of the aqueoussuspension through the electrical field increases residence time for adevice to achieve a desired level of aggregation without adjusting theflow path characteristics. Multiple passes could also achieve the sameresults with less physical equipment (shorter pipes, fewer electrodes,etc.). In some embodiments, the multiple pass system may run the entirevolume of the aqueous suspension through the electrical field multipletimes before treating a new volume of aqueous suspension in a batchprocess. In another embodiment, the multiple pass system may bleed off afirst portion of the aqueous suspension to be mixed with a volume ofuntreated aqueous suspension and recirculated through the electricalfield in a continuous recycle method, while a second portion continuesto the separation device or tank. In some embodiments, the secondportion contains a higher content of aggregated microorganisms than thefirst portion before the first portion is recirculated. In someembodiments, the volume of the aqueous suspension that is bled off andrecirculated is determined by a computer controlled system comprisingsensors. The sensors may comprise turbidity and/or density sensorslocated at the inlet and exit of the flow path comprising the electricalfield. The output from the sensors may be used to control therecirculation of the aqueous suspension based on the sensor outputmeeting a certain threshold turbidity/density value or change inturbidity/density value.

In some embodiments, the temperature of the aqueous suspension can alsobe adjusted to control the specific gravity of the water relative to themicroorganism. In such embodiments, as the liquid medium (typicallycomposed primarily of water) is heated or cooled, alterations to theliquid medium hydrogen density occurs. This alteration of density canallow a normally less dense material to sink. This alteration, accordingto some embodiments, also allows easier harvesting of the aggregatedmicroorganism. In a simplified description used to illustrate a heattransfer, according to some embodiments, between the outer walls of thecathode 106 and/or anode 104 and into the liquid medium/biomass duringthe electrical field application process in a method for harvestingcellular mass and debris from an aqueous solution containingmicroorganisms is disclosed below. In some embodiments, an appliedheating device attaches to the outside wall surfaces of the cathode andthe anode, which allows heat transfer to penetrate into the aqueousslurry. According to various embodiments, changes to the specificgravity of the liquid medium, which is mainly composed of water, byheating allows alteration in its compound structures which is mainly dueto alterations to the hydrogen element which when altered, lessens thewater density. In such embodiments, this density change allows anormally less dense material contained within a water column to sink or,in some embodiments, an aggregated mass of microorganisms to sink. Insome embodiments, a heat exchanger device attached to the outside wallsof the cathode and the anode, allows heat to transfer out of theelectrodes and/or aqueous slurry. In such embodiments, the temperatureof the aqueous slurry may be controlled to maintain the microorganismsin a desired condition.

According to embodiments wherein cavitation is used, a micron mixingdevice, such as a static mixer or other suitable device such as a highthroughput stirrer, blade mixer or other mixing device is used toproduce a foam layer composed of microbubbles within a liquid mediumcontaining aggregated microorganisms. According to such embodiments, anydevice suitable for generating microbubbles, however, can be used. Insuch embodiments, following micronization, the homogenized mixturebegins to rise and float upwards. According to such embodiments, as thismixture passes upwards through the liquid column, the aggregatedmicroorganisms freely attach to the rising bubbles, or due to bubblecollision, rise to the surface.

Once the foam layer containing these aggregated microorganisms has risento the top of the liquid column as described with reference to someembodiments, the valuable microorganisms now can be easily skimmed fromthe surface of the liquid medium and deposited into a harvest tank forlater product refinement or other subsequent processes according tovarious embodiments. According to some embodiments, once the foam layerrises to the top of the secondary tank, the water content trapped withinthe foam layer generally results in less than 10% of the original liquidmass. Trapped within the foam, according to such embodiments, are theaggregated microorganisms, and the foam is easily floated or skimmed offthe surface of the liquid medium. According to various embodiments, thisprocess uses only dewatering of the foam, rather than evaporating thetotal liquid volume needed for conventional harvest purposes. Suchembodiments drastically reduce the dewatering process, energy and/or anychemical inputs while increasing harvest yield and efficiency as well aspurity. Further, in such embodiments, water can be recycled to thegrowth chamber or removed from the system. Likewise, microorganisms canbe harvested at any appropriate time, including, for example, daily(batch harvesting) according to various embodiments. In another exampleor alternative embodiments, microorganisms are harvested continuously(e.g., a slow, constant harvest).

According to various embodiments, once the liquid medium has achievedpassage through the electrical field, it is allowed to flow over into asecondary or separation tank (or directly into a device that is locatednear the bottom of the tank). In such embodiments adapted fordewatering, the secondary tank is a tank containing a micron bubbledevice or having a micron bubble device attached for desiredmicroorganism separation and dewatering. According to such embodiments,after aggregation, a static mixer or other suitable device (e.g., anystatic mixer or device which accomplishes a similar effect of producingmicrobubbles) is used and is located at the lowest point within asecondary or separation tank. When activated, the static mixer producesa series of micron bubbles resulting in a foam layer that developswithin the liquid medium. As the liquid medium is continuously pumpedthrough the micro mixer, according to various embodiments, bubbled foamlayers radiate outwards through the liquid and begin to rise and floatupwards. In such embodiments, the aggregated microorganisms suspendedwithin the liquid medium attach to the micron bubbles floating upwardsto the surface.

According to various embodiments, a lower mounting location for a micronmixer when in association with secondary tank and containing apreviously treated biomass suspended within a liquid medium. In suchembodiments, the liquid medium is then allowed to flow through a lowersecondary tank outlet where it is directed to flow through conduithaving a directional flow relationship with a liquid pump. Furtheraccording to such embodiments, and due to pumping action, the liquid isallowed a single pass through, or to re-circulate through the micronmixer via a micron mixer inlet opening. In embodiments wherein theliquid continues to cyclically flow through micron mixer, microscopicbubbles are increasingly produced relative to each cycle. In suchembodiments, micro bubbles radiate outwards within the liquid column,forming a foam layer. As the process continues according to certainembodiments, the composed layer starts to rise upwards towards thesurface of the liquid column. In some embodiments, once the foam layerstarts its upward journey towards the surface of the liquid column, thepump is shut down, and thus the micronization process is complete.According to such embodiments, this allows all micron bubbles producedat the lower exit point of the micron mixer to rise to the surface, and,as they do, they start collecting aggregated microorganisms in theliquid medium. In various embodiments, the aggregated microorganismsadhere to the micron bubbles floating upwards towards the surface. Insome embodiments, pump remains on and continues to produce additionalmicron bubbles even after the foam layer starts its upward journey.According to such embodiments, the system is allowed to continuallyprocess an ongoing flow being introduced to the secondary or separationtank.

A method according to various embodiments for harvesting a foam layercontaining approximately ten percent (10%) of the original liquid mediummass/biomass is described below. According to such embodiments, as thefoam layer containing the aggregated microorganisms rises to the surfaceof the liquid medium, a skimming device can be used to remove the foamlayer from the surface of liquid medium. In various embodiments, theskimming device located at the surface area of the secondary tank allowsthe foam layer to be pushed over the side wall of the secondary tank andinto a harvesting container where the foam layer is allowed toaccumulate for further substance harvesting procedures.

Chemical and Electric Field Aggregation Combination Embodiments

In some embodiments, any of the apparatuses, systems and methods foraggregating microorganisms contained in an aqueous suspension using anelectrical field may be combined with a method using a chemicalaggregating agent. In some embodiments the chemical aggregating agentfacilitates the aggregation of the microorganisms chemically, and inother embodiments the chemical aggregating agent improves the electricalconductivity of the aqueous suspension to facilitate the aggregation ofthe microorganisms electrically (e.g. change in surface charge). Theaggregating agents may include, but are not limited to, salt, alum,aluminum chlorohydrate, aluminum sulfate, calcium oxide calciumhydroxide, iron (III) chloride, iron (II) sulfate, polyacrylamide,polyDADMAC, sodium aluminate, sodium silicate, chitosan, Moringaoleifera seeds, papain, strychnos seeds, isinglass, and combinationsthereof. Specific binding agents to one or more components of themicroorganism may also be used. The chemical aggregating agent may actdirectly on the microorganism being aggregated or it may enhance theactivity of electroaggregation or acoustic aggregation.

Acoustic Energy Embodiments

In addition to the use of electrical energy to aggregate and separatemicroorganisms in a flowing aqueous culture medium, acoustic energy alsoprovides a chemical free method of inducing concentration and separationof microorganisms in a flowing aqueous culture medium. Instead of usingelectrical energy to affect the surface charge of the microorganism,electrical energy can be used by a function generator to produce a radiofrequency signal which is converted to acoustic energy by transducers.Transducers in contact with the tube or channel through which theaqueous culture medium is flowing form a standing wave of acousticpressure within the tube by vibrating the tube. The standing wave ofacoustic pressure varies the pressure within the tube, creating areas ofhigh pressure and nodes of low or minima pressure. When an aqueousmedium comprising microorganisms flow through the standing waves,microorganisms may be pushed towards the minima pressure nodes. Byaggregating the microorganisms at the minima pressure nodes, themicroorganisms can be concentrated in a consistent location forcoagulation, flocculation and/or separation from the medium.

In one exemplary embodiment, an acoustic energy apparatus comprises: apower source, a radio frequency signal (function) generator, at leastone transducer in contact with a tube or channel. In some embodiments,the standing wave is created from the combination or superimposing ofmultiple out of phase acoustic pressure waves from multiple transducers.In some embodiments, the standing wave is created from the combinationof superimposing out of phase acoustic pressure waves from a transducerand a reflector. In some embodiments, the transducer creates a wavewhich travels across diameter of the tube or channel without reflection.

In the embodiments with a standing wave, at least one minima pressurenode may be created at the central axis of the tube, off center of thecentral axis of the tube, or along the walls of the tube. In someembodiments, there is a single minima pressure node, while in otherembodiments there are multiple minima pressure nodes. The wavelength ofthe standing wave in relation to the diameter of the tube or channelwill dictate the location and number of the minima pressure node(s). Inone non-limiting example, the diameter of the tube or channel is onehalf the wavelength of the standing wave and produces a minima pressurenode at the central axis of the tube or channel. The number of minimanodes will increase as the wavelength decreases. The higher pressureportions of the standing wave push the microorganisms suspended in theliquid medium to the location of the minima pressure nodes.

In some embodiments, a traveling or sweeping wave is used which hasminima pressure nodes which move or translate across the liquid medium.The pressure of the wave traveling or sweeping across the diameter ofthe tube pushes the microorganisms against one surface of the tube. Infurther embodiments, the direction of the traveling wave may be changedto move the biasing location of the microorganisms to another surfacelocation of the tube.

The liquid and particles in the aqueous culture medium of a differentsize and/or acoustic impedance than the microorganisms targeted by theacoustic energy will continue to fill the volume of the tube outside ofthe minima pressure node. By biasing the location of the targetedmicroorganisms within the tube, at least one collector or collectioninlet can be located in line with the biased location (e.g. center oftube, along one surface of the tube) to receive the microorganisms andseparate the microorganisms from the aqueous medium. The collector maycomprise a separate inlet located within the tube, or the tube may splitinto multiple flow paths with at least one of the branches comprisingthe collector.

The wave characteristics may be manipulated or tuned through theelectrical signal power source, the radio frequency (function)generator, a power amplifier, and/or the transducers. The acoustic waveswill affect particles differently based on their size and/or acousticimpedance. Acoustic impedance is determined by the particle shape, size,cell wall composition, physiological state, and compressibility.Examples of particles in the aqueous medium that have different sizesand/or acoustic impedances include, but are not limited to: maturemicroalgae in oil phase; younger microalgae in growth phase; differentspecies of microalgae; extraneous particulate matter; contaminants,predators, and competitors of microalgae such as grazers, rotifers,fungi, bacteria, viruses, cells or parts of living organisms, non-livingcell debris, and suspended organic matter. By tuning the characteristicsof the wave, particles of different size and/or acoustic impedance maybe targeted and biased to a location in a tube. Selectively biasing theparticles to a location aids in the removal of the particles from theaqueous medium for further processing of the particles and separates onegroup of particles from another. The system may be used for positive ornegative selection with either the target particles or the non-targetparticles being removed selectively. While the specification isdescribed as removing the desired aggregated particles from the liquid,it may equally be applied to removing undesired particles/contaminants.As such the liquid may be returned for additional cell growth or furtherprocessed to dewater the desired microorganisms or other particles.

The tube may comprise any material with a natural resonance frequencysuitable to create standing waves with minima pressure nodes or transmita traveling wave such as, but not limited to, glass, plastic, metals,crystalline solids, and quartz. In the creation of the standing waves,the entire length of the tube is excited by the transducer in contactwith the tube as the acoustic signal produced by the transducer isconverted into acoustic radiation pressure. The thickness of the tubemay affect the natural resonance frequency of the tube. The flow throughthe tube may be essentially laminar, and the flow rate may be controlledby pumping, gravity, valves, or the flow path geometry. The tube mayhave a circular, oval or elipitical, rectangular, or polygonalcross-section.

The at least one transducer is coupled to the tube, and receives a radiofrequency signal for conversion into an acoustic energy signal. The atleast one transducer may comprise any suitable material for producing anacoustic energy signal from a radio frequency signal such as, but notlimited to, piezoceramic, peizosalt, peizopolymer, piezocrystal,magnetostrictive, electromagnetic transducers, and lead zirconatetitanate. In some embodiments, multiple transducers may be used to tunethe frequency and provide electronic feedback, such as a pair oftransducers on opposing sides of the tube or channel. A reflector orreflection membrane may be used with a single transducer to create astanding wave within a tube or channel. The reflector may comprise anymaterial suitable for reflecting acoustic waves such as, but not limitedto, mylar, glass mica, and polymers.

The radio frequency signal generator may comprise a function generator.In some embodiments the radio frequency signal produced by the generatoris amplified by a power amplifier before transmission to the at leastone transducers. The frequencies may range from 10 kHz to 100 MHz. Thefrequency selected may be dictated by the desired function of theacoustic waves. Low frequencies may be used for the effect of inhibitingcyanobacteria growth in the aqueous medium. Ultrasonic frequencies mayalso be used for the effect of lysing or disrupting microalgae cellsthrough cavitation induced by acoustic energy. In some embodiments, thefrequency will be tuned to aggregate microorganisms at the minimapressure nodes without inhibiting growth or lysing/disrupting the cellsthrough cavitation.

The power may range from 0.05 W to 1 W for the aggregation ofmicroorganisms at the minima pressure nodes without inhibiting growth orlysing/disrupting the cells. In other embodiments, a higher power valuemay be used to inhibit growth or lyse/disrupt the microorganisms. Thepower source may provide constant electrical power (such as directcurrent), oscillating electrical power (such as alternating current), ora pulsed electrical current, including micro-pulses, pico-pulses, andnano-pulses as previous described above. In one exemplary embodimentusing pulsed electrical current, the transducer receives pulses ofelectricity at a frequency higher than the standing wave, resulting inthe rapid starting and stopping of the acoustic energy in a highfrequency pulse. After traveling a distance through the medium, the highfrequency pulse evolves into a demodulated pulse which can excite thedesired mode of the standing acoustic wave.

In some embodiments, multiple transducers and collectors may be used ina series configuration along a length of the tube. In furtherembodiments, the multiple transducers and collectors concentrate thesame target particles for collection at multiple points. In otherembodiments, the multiple transducers and collectors concentratedifferent target particles for collection at multiple points. In someembodiments, multiple collectors may be placed at different locationsand the standing waves may be adjusted to move the minima pressure nodesto the different locations of the collectors, effectively activating andinactivating the collectors selectively. In some embodiments, a standingwave may be used to concentrate the target particles at a minimapressure node first, and then moved towards a collector using atravelling or sweeping wave second. Additionally, a plurality of tubeswhich apply acoustic energy to the aqueous medium may be connected in aseries or parallel arrangement as described above with the plurality ofanode and cathode circuits. The system may be used for positive ornegative selection with either the target particles or the non-targetparticles being removed selectively.

Combination Electroacoustic Embodiments

In some embodiments, the application of electrical energy, as describedabove, and acoustic energy can be used in combination in a singlesystem. In one embodiment, the system may switch back and forth betweenthe application of electrical energy and acoustic energy to the aqueoussuspension. In one embodiment, as illustrated in FIG. 20A, acousticenergy is applied to the aqueous medium comprising microorganisms firstto concentrate a target microorganism at a minima pressure node. Thetarget microorganism is then separated from the aqueous medium by acollector. Next, the separated target microorganisms are subjected to anelectrical field to affect the surface charge of the microorganisms tofurther aggregate the microorganisms into a more cohesive aggregatemass. The aqueous medium not separated by the collector may be divertedfor additional use (such as growth medium for a new culture ofmicroorganisms) or recycled through the system for further applicationof acoustic energy targeting the same microorganism or a differentparticle. Embodiments using electrical and acoustic energy incombination may provide for the first separation and aggregation ofmicroorganisms of a first characteristic in the aqueous culture medium,such as oil phase microalgae, a first species of microalgae, or a firstcontaminant/predator/competitor; and then the subsequent separations andaggregations of microorganisms of a different characteristic, such asgrowth phase microalgae, a second species of microalgae, or a secondcontaminant/predator/competitor. Embodiments using electrical andacoustic energy in combination provide an efficient method for:selectively separating and aggregating microalgae in different phaseswithin the same culture; selectively separating and aggregatingdifferent microalgae species which were co-cultured; selectivelycleaning a culture through separating and aggregating variousmicroorganisms, contaminants, predators, and competitors; andselectively cleaning a culture before aggregating the microorganisms.Acoustic energy can also be used to bias the algae to a certain locationand then tunable electrodes may be used to apply an electrical field tothe algae location in the most energy efficient manner.

In another embodiment, electrical energy is applied to the aqueoussuspension comprising microorganisms first to aggregate themicroorganisms into larger aggregate masses, as illustrated in FIG. 20B.Next, acoustic energy is applied to concentrate the aggregatemicroorganism masses at the minima pressure nodes and separating thelarger aggregate masses from the aqueous medium through a collector. Theaqueous medium not separated by the collector can be recycled throughthe system for further application of electrical energy for aggregation.This embodiment provides an efficient method for creating stronger bondsbetween the microorganisms concentrated at the minima pressure nodes bythe acoustic energy.

In some embodiments, a tube with a rectangular shaped cross-section anda pair of plate electrodes with spacers may be joined to form acontinuous tube with a rectangular shaped cross-section. In someembodiments, a tube with a circular cross-section and a pair ofsemi-circular shaped electrodes with spacers may be joined to form acontinuous tube with a circular shaped cross-section. The continuoustube may form a single tubular structure with a uniform cross-sectionfor applying both acoustic energy and electrical energy in line in analternating fashion. In some embodiments an elastomeric spacer joins theacoustic and electric application sections to reduce vibration in theelectrical application section and insulate the acoustic applicationsection from an electrical charge.

In some embodiments, the electrical and acoustic energy are applied tothe aqueous suspension simultaneously. Referring to FIG. 21, a tube 2100forms the channel for flowing an aqueous suspension comprisingmicroorganisms. The tube 2100 may comprise any suitable material thatcan be excited by transducers 2103, 2104 to produce a standing wave ofacoustic pressure within the interior of the tube. Housed within thetube is an anode 2101 and a cathode 2102 facing each other and runninglongitudinally through the tube. The anode 2101 and cathode 2102 arespaced to allow a gap between the electrodes in which the minimapressure node 2110 of the acoustic pressure wave is located and theaqueous medium flows through. The transducers 2103, 2104 may create astanding wave within the tube 2100 concurrently with the anode 2101 andcathode 2102 pair producing an electric field within the tube as theaqueous culture suspension comprising microorganisms flows through thetube. The standing wave forms anti-nodes of acoustic pressure wave 2105,2106. Referring to FIG. 22, the channel for flowing an aqueous solutioncomprising microorganisms is defined by a spaced anode 2201 and cathode2202 pair and insulators 2203 as described above in the rectangularchannel embodiment above. Transducers 2204 may be coupled to the anode2201 and cathode 2202 to produce a standing wave of acoustic pressurewithin the channel by vibrating the anode 2201 and cathode 2202, andform a minima pressure node between the anode 2201 and cathode 2202concurrently with the anode 2201 and cathode 2202 pair producing anelectrical field within the channel as tube as the aqueous culturesuspension comprising microorganisms flows through the channel.

Vibration Energy Recovery

In embodiments using acoustic energy, a piezoelectric vibrationharvester may be coupled to the tube. The piezoelectric vibrationharvester captures some of the mechanical vibration energy used toproduce the standing wave and converts the vibration energy intoelectrical current. The electrical current may be alternating current(AC) or may be converted from AC into direct current (DC). Theelectrical current may form a power source that can be transmittedwirelessly to sensors, such as flow rate, density, or turbidity sensorson the same aggregating apparatus. The piezoelectric vibrationharvesters may be designed or commercially available from companies suchas Mide and Perpetuum.

Advantages of using a system with acoustic and electrical energyinclude: the avoidance of fouling issues common with filters, reductionin the application of shear forces to microorganisms which are commonwith mechanical systems such as centrifuges, reduction in moving or wearparts that lead to mechanical failure due to friction, and thecapability of continuous operation. The application of acoustic and/orelectric energy also results in biasing, concentration, and/oraggregation of microalgae in a short time period, such as minutes orseconds. Both the flow rate and biomass concentration of the aqueousmedium affect the efficiency of the aggregating methods using acousticand/or electrical energy, therefore a two pronged approach which usesboth methods in various combinations can increase the system efficiencyby 1) increasing the size of the particles through electricalaggregation for influence by the acoustic pressure, 2) moving theparticles within closer proximity to each other with acoustic pressurefor quicker attraction between the particles once the electrical energyalters the surface charge, and 3) aggregating the particles throughacoustic pressure into an optimal location for receiving an electricalfield. Additionally, biasing particles to a location in the tube orchannel away from the surfaces of the tube or channel may preventbiofouling of the tube or channel surfaces. These techniques may be usedin combination with any other conventional technique for removingparticles, such as filtering, settling, flocculation, centrifugation orother particle aggregation technique. Such may be used either before orafter the techniques of the present invention.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof and that theforegoing description is intended to illustrate and not limit the scopeof the invention. Other aspects, advantages and modifications within thescope of the invention will be apparent to those skilled in the art towhich the invention pertains.

What is claimed is:
 1. An apparatus for aggregating microorganisms in anaqueous suspension, comprising: a. a vessel configured to contain anaqueous suspension of microorganisms and configured for fluidcommunication with a housing; b. at least one first electrical conductorconfigured as a cathode disposed within the housing; c. at least onesecond electrical conductor configured as an anode disposed within thehousing; d. at least one third electrical conductor configured as acollector electrode disposed within the housing and adjacent to the atleast one first electrical conductor; e. at least one fourth electricalconductor configured as a control electrode disposed within the housingand adjacent to the at least one first electrical conductor, wherein theat least one first electrical conductor is at least partially surroundedby the at least one second electrical conductor such that a channel isdefined between an exterior surface of the at least one first electricalconductor and an interior surface of the at least one second electricalconductor, providing a fluid flow path configured for receiving theaqueous suspension from the vessel; and f. at least one electrical powersource operably connected to the at least one first electricalconductor, second electrical conductor, third electrical conductor, andfourth electrical conductor, wherein an electrical field is created byproviding an electrical current from the electrical power source to theat least one first electrical conductor, second electrical conductor,third electrical conductor, and fourth electrical conductor wherein across-sectional area of the electrical field is adjustable based on thecurrent applied to the at least one third electrical conductor and theat least one fourth electrical conductor.
 2. The apparatus of claim 2,further comprising a separation tank configured to receive the aqueoussuspension exiting the fluid flow path.
 3. The apparatus of claim 2,wherein the at least one first electrical conductor has a circularcross-section or a polygonal cross-section.
 4. The apparatus of claim 2,wherein the at least one second electrical conductor has a curvedsemi-circular cross-section or a circular cross-section.
 5. Theapparatus of claim 2, wherein the at least one third electricalconductor has a circular cross-section, a polygonal cross-section, av-shaped cross section, or a curved cross section.
 6. The apparatus ofclaim 2, wherein the at least one fourth electrical conductor has acircular cross-section or a polygonal cross-section.
 7. The apparatus ofclaim 2, wherein the at least one third electrical conductor and the atleast one second electrical conductor have a positive potential relativeto the at least one first electrical conductor, the at least one secondelectrical conductor has a larger positive potential than the at leastone third electrical conductor, and the at least one fourth electricalconductor has a negative potential relative to the at least one firstelectrical conductor.
 8. The apparatus of claim 7, wherein thecross-sectional area of the electrical field is adjusted by increasingor decreasing the negative potential of the at least one thirdelectrical conductor.
 9. The apparatus of claim 7, wherein thecross-sectional area of the electrical field is adjusted by increasingor decreasing the negative potential of the at least one fourthelectrical conductor.
 10. The apparatus of claim 7, wherein thecross-sectional area of the electrical field is adjusted by increasingor decreasing the negative potential of the at least one thirdelectrical conductor and at least one fourth electrical conductor. 11.The apparatus of claim 1, wherein the at least one electrical powersource provides continuous electrical current.
 12. The apparatus ofclaim 1, wherein the at least one electrical power source provides apulsed electrical current.
 13. A method for aggregating microorganismsin an aqueous suspension, comprising: a. flowing an aqueous suspensionscomprising microorganisms into an apparatus comprising: i. at least oneelectrical conductor with a first potential, at least one secondelectrical conductor with a second potential, at least one thirdelectrical conductor with a third potential, and at least one fourthelectrical conductor with a fourth potential, the at least one firstelectrical conductor being disposed such that a channel is definedbetween the at least one first electrical conductor and the at least onesecond electrical conductor, wherein the channel defines a fluid flowpath for the aqueous suspension; and ii. at least one electrical powersource operably connected to the at least one first electricalconductor, second electrical conductor, third electrical conductor, andfourth electrical conductor, wherein an electrical field is created byproviding an electrical current from the electrical power source to theat least one first electrical conductor, second electrical conductor,third electrical conductor, and fourth electrical conductor; b. applyingan electrical current to the at least one first electrical conductor,second electrical conductor, third electrical conductor, fourthelectrical, and aqueous suspension whereby the surface charge of themicroorganisms is treated and the microorganisms aggregate withsimilarly treated microorganisms in the aqueous suspension withoutdisrupting the cell membrane; and c. adjusting the at least one powersource to change the potential of at least one of the third electricalconductor and fourth electrical conductor, wherein the change inpotential of the at least one third electrical conductor or fourthelectrical conductor changes the cross-sectional area of the electricalfield.
 14. The method of claim 13, wherein the at least one thirdelectrical conductor and the at least one second electrical conductorhave a positive potential relative to the at least one first electricalconductor, the at least one second electrical conductor has a largerpositive potential than the at least one third electrical conductor, andthe at least one fourth electrical conductor has a negative potentialrelative to the at least one first electrical conductor.
 15. The methodof claim 13, wherein the at least one electrical power source providescontinuous electrical current.
 16. The method of claim 13, wherein theat least one electrical power source provides a pulsed electricalcurrent.